Testwiki:Manual of Style/Dates and numbers ಇಗೆ ಮೂಲವನ್ನು ವಿಕ್ಷಿಸಿ

{{Style-guideline|WP:MOSNUM|WP:DATE|MOS:NUM}}
{{Style}}<!--
-- PLEASE MAKE MINOR CHANGES TO THIS TEXT ALSO TO THE EQUIVALENT TEXT AT MOS. MORE SIGNIFICANT CHANGES, ESPECIALLY IN POLICY, NEED TO BE FLAGGED AT MOS TALK PAGE BEFORE IMPLEMENTATION HERE AND AT MOS, UNLESS THEY INVOLVE SECTIONS HERE THAT HAVE NO EQUIVALENT AT MOS (e.g. GEOGRAPHICAL COORDINATES). --><!-- Please use "quotes" when mentioning units (as opposed to using units) instead of ''italics'' or '''bold''' to avoid confusion concerning their proper formatting. -->
This part of the '''[[Wikipedia:Manual of Style|Manual of Style]]''' helps editors to achieve consistency in the use and formatting of numbers, dates, times, measurements, currencies, and coordinates in Wikipedia articles. Consistency in style and formatting promotes clarity and cohesion; this is especially important within an article. The goal is to make the whole encyclopedia easier and more intuitive to use. Try to write so the text cannot be misunderstood, and take account of what is likely to be familiar to readers. The less that readers have to look up definitions, the easier the text will be to understand. 
Where this manual provides options, consistency should be maintained within an article unless there is a good reason to do otherwise. The [[Wikipedia:Arbitration Committee|Arbitration Committee]] has ruled that editors should not change an article from one guideline-defined style to another without a substantial reason unrelated to mere choice of style, and that revert-warring over optional styles is unacceptable.<ref>{{section link|Wikipedia:Requests for arbitration/Jguk|Principles}}, {{section link|Wikipedia:Requests for arbitration/jguk 2|Principles}}, and {{section link|Wikipedia:Requests for arbitration/Sortan|Principles}}</ref> If discussion cannot determine which style to use in an article, defer to the style used by the first major contributor.
 
==General notes==
===<span id="ExternException"></span>Quotations, titles, etc.===
{{see also|WP:MOSQUOTE}}
Quotations, titles of books and articles, and similar "imported" text should be faithfully reproduced, even if they employ formats or units inconsistent with these guidelines or with other formats in the same article. If necessary, clarify via ''[bracketed interpolation]'', article text, or footnotes.
* It is acceptable to change other date formats in the same article to provide consistency, so long as those changes would otherwise be acceptable.<!-- "to provide consistency" with what? Is this suggesting changing the article to match a quote or quotes?-->
===Non-breaking spaces===
Guidance on the use of [[non-breaking space]]s (also called "hard spaces"; ''markup:'' <code>{{t|nbsp}}</code> or <code>&amp;nbsp;</code>) is given in some of the sections below, though not all situations in which ''nbsp'' may be appropriate are described. {{t|nowrap}} may also be useful in some situations. For further information see {{section link|Wikipedia:Manual of Style|Non-breaking spaces}} and [[Wikipedia:Line-break handling]].
==Chronological items==
<!-- {{Split section|Manual of Style (time and dates)|discuss=Wikipedia Talk:Manual of Style (dates and numbers)#Split proposal}} -->
<!-- Temporarily commented out until a suitable destination is identified on the talk page -->
===<span id="Precise language"></span>Statements likely to become outdated===
{{Shortcut|WP:DATED|WP:EPHEMERAL}}
{{See also|Wikipedia:As of|Wikipedia:Manual of Style/Words to watch#Relative time references}}
Except on pages updated regularly (e.g. [[Wikipedia:How the Current events page works|current events]]), terms such as {{!xt|now}}, {{!xt|soon}}, {{!xt|currently}}, and {{!xt|recently}} should usually be avoided in favor of phrases such as {{xt|during the 1990s}} and {{xt|in August 1969}}. For future and current events, use phrases such as {{xt|as of {{CURRENTMONTHNAME}} {{CURRENTYEAR}}}} or {{xt|since the beginning of 2010}} to signal the time-dependence of the information. Or (for example) {{tlc|as of|{{CURRENTYEAR}}}} will produce the text {{xt|{{as of|{{CURRENTYEAR}}}}}} and adds the article to a category flagging it for periodic review.<!--though of course this will never happen--> However, do not replace (for example) {{xt|since the start of 2005}} with {{tlc|as of|2005}} because some information (the ''start'' of 2005) would be lost; advanced features of {{tlf|as of}} such as <code><nowiki>{{as of|2005|alt=since the start of 2005}}</nowiki></code> can be used in such circumstances.
Relative-time expressions are acceptable for very long periods, such as geological epochs: {{xt|Humans diverged from apes long ago, but [[wikiquote:Samuel Butler (novelist)#Miscellaneous|only recently developed state legislatures]].}}
===Time of day===
{{Shortcut|WP:MOSTIME|MOS:TIME}}
Context determines whether the [[12-hour clock|12-]] or [[24-hour clock|24-hour]] clock is used; in both, colons separate hours, minutes and seconds (e.g. {{xt|1:38:09{{nbsp}}pm}} or {{xt|13:38:09}}).
* '''12-hour clock times''' end with dotted or undotted lower-case ''a.m.'' or ''p.m.'', or ''am'' or ''pm'', preceded by a space (e.g. {{xt|2:30{{nbsp}}p.m.}} or {{xt|2:30{{nbsp}}pm}}, not {{!xt|2:30p.m.}} or {{!xt|2:30pm}}). Hours denoted by a single digit should not have a leading zero (e.g. {{xt|2:30{{nbsp}}p.m.}}, not {{!xt|02:30{{nbsp}}p.m.}}). A hard space (see [[#Non-breaking spaces|above]]) is advisable (<code>2:30&amp;nbsp;pm</code> or {{tlx|nowrap|2:30 p.m.}}). Use {{xt|noon}} and {{xt|midnight}} rather than {{!xt|12 pm}} and {{!xt|12 am}}; whether ''midnight'' refers to the start or the end of a date will need to be specified unless it is clear from the context.
* '''24-hour clock times''' have no a.m., p.m., noon or midnight suffix. Hours under 10 should have a leading zero (e.g. {{xt|08:15}}). {{xt|00:00}} refers to midnight at the start of a date, {{xt|12:00}} to noon, and {{xt|24:00}} to midnight at the end of a date, but "24" should not be used for the first hour of the next day (e.g. use {{xt|00:10}} for ten minutes after midnight, not {{!xt|24:10}}).
The numerical elements of times-of-day are figures ({{xt|12:45{{nbsp}}p.m.}}) rather than words ({{!xt|twelve forty-five p.m.}}) though conventional terms such as {{xt|noon}} and {{xt|midnight}} are acceptable (taking care, with the latter, to avoid possible date ambiguity in constructions such as ''midnight on July 17'').
====<span id="timezones"></span>Time zones====
{{shortcut|WP:TIMEZONE}}Give dates and times appropriate to the [[time zone]] where an event took place. For example, the date of the [[attack on Pearl Harbor]] should be December{{nbsp}}7, 1941 (Hawaii time/{{zwsp}}date). Give priority to the place at which the event had its most significant effects; for example, if a hacker based in Japan attacked a Pentagon computer in the US, use the time zone for the Pentagon, where the attack had its effect. In some cases the best solution may be to add the date and time in [[Coordinated Universal Time]] (UTC). For example:
:{{in5|2}}&bull;{{in5|2}} {{xt|8{{nbsp}}p.m. [[Eastern Standard Time (North America)|Eastern Standard Time]] on January{{nbsp}}15, 2001 (01:00{{nbsp}}UTC, January{{nbsp}}16)}}
Alternatively, include just the [[UTC offset]]:
:{{in5|2}}&bull;{{in5|2}}{{xt|21:00{{nbsp}}[[British Summer Time]] ([[UTC+1]]) on 27{{nbsp}}July 2012}}
Rarely, the time zone in which a historical event took place has since changed; for example, China to 1949 was divided into [[Historical time zones of China|five time zones]], whereas all of modern China is [[UTC+8]]. Similarly, the term "UTC" is not appropriate for dates before this system was adopted in 1961; [[Universal Time]] (UT) is the appropriate term for the mean time at the [[prime meridian (Greenwich)]] when it is unnecessary to specify the precise definition of the time scale. Be sure to show the UTC or offset appropriate to the clock time in use at the time of the event, not the modern time zone, if they differ.
=== <span id="dates"></span> Dates and years ===
{{shortcut|WP:YR|MOS:YEAR|WP:DATESNO|MOS:DATEFORMAT}}
These requirements do not apply to dates in quotations or titles. Special rules apply to citations; see {{section link|Wikipedia:Citing sources|Citation style}}.
==== Formats ====
===== <span id="Acceptable date formats"></span><span id="years"></span><span id="Years"></span> Date formats =====
{| class="wikitable"
|+ Acceptable date formats
|-
! width="160pt" | General use
! width="175pt" | {{nowrap|Only where brevity is required}} {{small|(references,<ref>See [[WP:CITESTYLE]].</ref> tables, lists, etc.)}}
!  Comments
|-
| {{xt|22{{nbsp}}August 2001}}
| {{xt|22{{nbsp}}Aug 2001}}
|
|-
| {{xt|August{{nbsp}}22, 2001}}
| {{xt|Aug{{nbsp}}22, 2001}}
| A comma follows the year unless followed by other punctuation:<ref>See [[MOS:COMMA]].</ref> {{ unordered list | {{xt|The weather on September 11, 2001, was clear and warm}} | {{xt|Everyone remembers July{{nbsp}}21, 1969{{mdashb}}when man landed on the Moon}} }}
|-
| {{xt|22{{nbsp}}August}}
| {{xt|22{{nbsp}}Aug}}
| rowspan=2 | Omit year only where there is no risk of ambiguity: {{ unordered list | {{xt|In 2013, Ramadan began on 10{{nbsp}}July and ended on 7{{nbsp}}August}} | {{xt|January{{nbsp}}1 is New Year's Day}} }}
|-
| {{xt|August{{nbsp}}22}} 
| {{xt|Aug{{nbsp}}22}}
|-
| <small>No equivalent for general use</small>
| {{xt|2001-08-22}}
| Use only with [[Gregorian calendar|Gregorian]] dates between 1583 and{{nbsp}}9999<ref>All-numeric {{small caps|yyyy-mm-dd}} dates might be assumed to follow the [[ISO 8601]] standard, which mandates the Gregorian calendar.</ref>
|}
{{shortcut|MOS:UNLINKYEARS|MOS:UNLINKDATES}}{{anchor|Date autoformatting|Autoformatting and linking}}{{anchor|Linking and autoformatting of dates}}
* The [[Wikipedia:Manual of Style/Dates and numbers/Date autoformatting|routine linking of dates]] is deprecated.<ref>This change was made August 24, 2008, on the basis of [[Wikipedia talk:Manual of Style (dates and numbers)/Archive D6#Again calling for date linking to be deprecated|this archived discussion]]. It was ratified in two December 2008 RfCs [[Wikipedia:Manual of Style/Dates and numbers/Three proposals for change to MOSNUM]] and [[Wikipedia:Manual of Style/Dates and numbers/Date Linking RFC]]</ref> Dates should be linked only when they are germane to the subject, as discussed at {{section link|Wikipedia:Linking|Chronological items}}.
* For issues related to dates in sortable tables, see ''[[Help:Sorting#Date sorting problems|Date sorting problems]]'' or consider using {{nowrap|{{tlx|sort|2008-11-01|1 Nov 2008}}}} or {{nowrap|{{tlx|dts|Nov 1, 2008}}.}}
* Phrases such as {{xt|[[Fourth of July]]}} (or {{xt|July{{nbsp}}Fourth}}, but not {{!xt|July{{nbsp}}4th}}), {{xt|[[Cinco de Mayo]]}}, {{xt|[[Seventh of March Speech]]}} and {{xt|[[Independence Day (Brazil)|Sete de Setembro]]}} are proper names, to which rules for dates do not apply ({{xt|Every Fourth of July celebration includes fireworks}}).
{{anchor|Unacceptable date formats}}{{Shortcut|WP:BADDATEFORMAT|MOS:BADDATEFORMAT}}
{| class="wikitable"
|+ Unacceptable date formats (except in [[#ExternException|external titles and quotes]])
|-
! width="140pt" | [[File:Yes check.svg|11px|link=|alt=]] Acceptable
! width="140pt" | [[File:X mark.svg|11px|link=|alt=]] Unacceptable
! width="420pt" | Comments
|-
| rowspan=3 | {{xt|9{{nbsp}}June}} {{small|''or''}} {{xt|June{{nbsp}}9}}
| {{!xt|June 9th}}<br />{{!xt|9th June}}<br />{{nowrap|{{!xt|the 9th of June}}}}
| Do not use ''1st'', ''2nd'', ''3rd'',{{nbsp}}etc.
|-
| {{!xt|9'''.'''<!--<<bold to make dot a smidge more obvious--> June}}
| Do not add a dot to the{{nbsp}}day
|-
| {{!xt|09 June}}<br />{{!xt|June 09}}
| rowspan=2 | Do not "zero-pad" month or day, except in all-numeric {{nowrap|({{small caps|yyyy-mm-dd}}) format}}
|-
| rowspan="3"| {{xt|2007-04-15}}
| {{!xt|2007-4-15}}
|-
| {{!xt|2007/04/15}}
| Do not use separators other than{{nbsp}}hyphen
|-
| {{!xt|15-04-2007}}<br />{{!xt|04-15-2007}}<!-- the specific combination of values "04" and "15" (one below 12, the other above 12) used in these "Unacceptable" examples was chosen to allow there to be a single unambiguous entry in the "Acceptable" column--> 
| Do not use {{nowrap|{{small caps|dd-mm-yyyy}}}} or {{nowrap|{{small caps|mm-dd-yyyy}}}}<!--intentionally omitting YYYY-DD-MM from list of no-no formats, because an editor perverse enough to consider that is beyond the help of MOS anyway--> formats, as they are ambiguous for {{nowrap|some dates{{efn-ua|These formats cannot be distinguished on sight, because there are usages in which {{nowrap|03-04-2007}} represents March{{nbsp}}4, and other usages in which it represents April{{nbsp}}3. In contrast there is no common usage in which {{nowrap|2007-04-03}} represents anything other than April{{nbsp}}3. For consistency the designation of {{nowrap|{{small caps|yyyy-mm-dd}}}} as the only acceptable all-numeric format applies even where the set of dates involved (e.g. in a particular article) all have "day" greater than 12, so that e.g. {{nowrap|04-15-2007}} would unambiguously represent April{{nbsp}}15.}} }}
|-
| rowspan=2| {{xt|July 2001}}
| {{!xt|7-2001}}<br />{{!xt|07-2001}}<br />{{!xt|2001 July}}<br />{{!xt|July of 2001}}
| Do not use these{{nbsp}}formats
|-
| {{!xt|July''',''' 2001}}
| rowspan=2| No comma between month and{{nbsp}}year
|-
| {{xt|3{{nbsp}}July 2001}}
| {{!xt|3 July''',''' 2001}}
|-
| {{xt|July{{nbsp}}3''',''' 2001}}
| {{!xt|July 3 2001}}
| Comma required between day and{{nbsp}}year
|-
| {{xt|{{nowrap|the 2002 elections}}}}
| {{!xt|the{{nbsp}}'''{{'}}'''02 elections}}
| Do not use an apostrophe to abbreviate{{nbsp}}year
|-
| {{xt|Copyright 2002}}
| {{!xt|Copyright MMII}}
| [[Roman numerals]] are not normally used for{{nbsp}}dates
|-
| {{xt|2001}}
| {{!xt|{{nowrap|Two thousand one}}}}
|  rowspan=2| Years and days of the month are not normally written in{{nbsp}}words
|-
| {{nowrap|{{xt|May{{nbsp}}1}}{{small|'' or ''}}{{xt|1{{nbsp}}May}}}}
| {{!xt|the first of May}}<br>{{!xt|May the first}}
|-
| {{xt|sold in 1995}}
| {{!xt|{{nowrap|sold in the year 1995}}}}
| Use "in the year" only where needed for clarity {{nowrap|({{xt|About 1800{{nbsp}}ships arrived in the year 1801}})}}
|}
''Note to table:''
{{reflist|group=upper-alpha}}
=====<span id="Format consistency"></span>Consistency=====
{{shortcut|MOS:DATEUNIFY}}
* '''Dates in article body text''' should all use the same format: {{xt|She fell ill on 25{{nbsp}}June 2005 and died on 28{{nbsp}}June}}, but not {{!xt|She fell ill on 25{{nbsp}}June 2005 and died on June{{nbsp}}28}}.
* '''Publication dates''' in an article's citations should all use the same format, which may be
:*any format from the [[MOS:DATEFORMAT|"Acceptable date formats" table]], or
:*formats required by the [[WP:CITESTYLE|citation style]] being used.
:*However, all-numeric date formats other than {{nowrap|{{small caps|yyyy-mm-dd}}}} must still be avoided.
:For example, a single article might contain either:
::{{xt|Jones, J. (20{{nbsp}}Sep 2008)}}, or
::{{xt|Smith, J. (Sep 2002)}}
:but not both:
::{{!xt|Jones, J. (20{{nbsp}}Sep 2008)}}, and
::{{!xt|Smith, J. (September 2002)}}
* '''Access and archive dates''' in an article's citations should all use the same format, which may be:
:*{{nowrap|{{small caps|yyyy-mm-dd}}}}, or
:*the format used for publication dates in the article, or
:*the format required for the citation style adopted in the article.
:For example, a single article might contain either:
::{{xt|Jones, J. (20{{nbsp}}Sep 2008){{nbsp}}... Retrieved 5{{nbsp}}Feb 2009.}}, or
::{{xt|Jones, J. (20{{nbsp}}Sep 2008){{nbsp}}... Retrieved 2009-02-05.}}
:but not more than one of:
::{{!xt|Jones, J. (20{{nbsp}}Sep 2008){{nbsp}}... Retrieved 5{{nbsp}}February 2009.}},
::{{!xt|Jones, J. (20{{nbsp}}Sep 2008){{nbsp}}... Retrieved Feb{{nbsp}}5, 2009.}}, and
::{{!xt|Jones, J. (20{{nbsp}}Sep 2008){{nbsp}}... Retrieved February{{nbsp}}5, 2009.}}
=====Strong national ties to a topic=====
{{shortcut|WP:STRONGNAT}}
{{See also|Wikipedia:Manual of Style#Strong national ties to a topic}}
* Articles on topics with strong ties to a particular English-speaking country should generally use the more common date format for that nation. For the United States, this is month before day; for most others, it is day before month. Articles related to Canada may use either format consistently.
* Sometimes the customary format differs from the usual national one: for example, articles on the modern US military use day before month, in accordance with military usage.
=====<span id="Retaining the existing format"></span>Retaining existing format=====
{{shortcut|WP:DATERET}}
{{See also|Wikipedia:Manual of Style#Retaining the existing variety|l1=Wikipedia:Manual of Style: Retaining the existing variety}}
* If an article has evolved using predominantly one format, the whole article should conform to it, unless there are reasons for changing it based on strong national ties to the topic or consensus on article talk.
* The date format chosen by the first major contributor in the early stages of an article should continue to be used, unless there is reason to change it based on strong national ties to the topic or consensus on article talk.
* Where an article has shown no clear sign of which format is used, the first person to insert a date is equivalent to "the first major contributor".
====<span id="Year numbering systems"></span><span id="Eras and other very long periods"></span>Era style====
{{shortcut|WP:ERA|WP:BCE}}
* The default [[calendar era]] is the [[Dionysian era|Western Dionysian era system]], a year numbering system also known as the Western Christian era (represented by {{xt|[[Anno Domini|BC and AD]]}}), or the [[Common Era]] (represented by {{xt|[[Common Era|BCE and CE]]}}).
** BC and AD are the traditional ways of referring to this era. BCE and CE are common in some scholarly texts and religious writings. Either convention may be appropriate.
*** Do not change the established era style in an article unless there are reasons specific to its content. Seek consensus on the talk page ''before'' making the change. Open the discussion under a subhead that uses the word "era". Briefly state why the style is inappropriate for the article in question. A personal or categorical preference for one era style over the other is not justification for making a change.
*** BCE and CE or BC and AD are written in upper case, unspaced, without periods (full stops), and separated from the year number by a space ({{xt|5{{nbsp}}BC}}, not {{!xt|5BC}}). It is advisable to use a [[WP:NBSP|non-breaking space]].
***  {{xt|AD}} may appear before or after a year ({{xt|AD{{nbsp}}106}}, {{xt|106{{nbsp}}AD}}); the other abbreviations appear after ({{xt|106{{nbsp}}CE}}, {{xt|3700{{nbsp}}BCE}}, {{xt|3700{{nbsp}}BC}}).
*** Do not use CE or AD unless required to avoid ambiguity (e.g. "The Norman Conquest took place in {{xt|1066}}" not {{!xt|1066{{nbsp}}CE}} nor {{!xt|AD{{nbsp}}1066}}).  On the other hand, {{xt|"[[Plotinus]] was a philosopher living at the end of the 3rd century AD"}} will avoid unnecessary confusion. Also, in {{xt|"He did not become king until 55{{nbsp}}CE"}} the era marker makes it clear that "55" does not refer to his age. Alternatively, {{xt|"He did not become king until the year 55."}}
*** Use either the BC{{ndash}}AD or the BCE{{ndash}}CE notation consistently within the same article. Exception: do not change [[MOS:QUOTE|direct quotations]].
* '''Uncalibrated (bce) radiocarbon dates:''' Some source materials will indicate whether a date is calibrated or not simply by a change in capitalisation; this is often a source of confusion for the unwary reader. Do not give [[Radiocarbon dating#Calibration|uncalibrated radiocarbon dates]] (represented by the lower-case ''bce'' unit, occasionally ''bc'' or ''b.c.'' in some sources), except in directly quoted material, and even then include a footnote, a square-bracketed editor's note [like this], or other indication to the reader what the calibrated date is, or at least that the date is uncalibrated. Calibrated and uncalibrated dates can diverge surprisingly widely, and the average reader does not recognise the distinction between ''bce'' and ''BCE'' or ''BC''.
* '''BP''': In scientific and academic contexts, [[before present|BP]] (before present) is often used. This is calibrated from January 1, 1950, not from the date of publication, though the latter introduces an insignificant error when the date is distant or an approximation (18,000{{nbsp}}BP). BP years are given as {{xt|18,000{{nbsp}}BP}} or spelled out as {{xt|18,000{{nbsp}}years before present}} (not {{!xt|18,000{{nbsp}}YBP}}, {{!xt|18,000 before present}}, {{!xt|18,000 years before the present}}, or similar).  Do not convert other notations to or from BP unless you are certain of what you are doing. A safer and simpler alternative may be to use "ya (years ago)".
* '''Other era systems''' may be appropriate in an article. In such cases, dates should be followed by a conversion to Dionysian (or vice versa) and the first instance should be linked: "Qasr-al-Khalifa was built in 221{{nbsp}}[[Hijri year|AH]] (836{{nbsp}}CE)" or "in 836{{nbsp}}AD (221{{nbsp}}[[Hijri year|AH]])". 
** [[Astronomical year numbering]] follows the Common Era and does not require conversion, but the first instance of a non-positive year should still be linked: "{{xt|The March equinox passed into Pisces in [[Astronomical year numbering|year −67]].}}"
====Julian and Gregorian calendars====
{{shortcut|WP:OSNS|WP:JG}}
{{see also|Old Style and New Style dates}}
A date can be given in any appropriate calendar, as long it is (at the minimum) given in the [[Julian calendar]] or the [[Gregorian calendar]] or both, as described below. For example, an article on the early [[history of Islam]] may give dates in both [[Islamic calendar|Islamic]] and Julian calendars. Where a calendar other than the Julian or Gregorian is used, the article must make this clear.
* Current events are dated using the Gregorian calendar.
* Dates of events in countries using the Gregorian calendar at that time are given in the Gregorian calendar. This includes some of the [[Gregorian calendar#Timeline|Continent of Europe from 1582]], the [[British Empire]] from 14{{nbsp}}September 1752, and Russia from 14{{nbsp}}February 1918 (see [[Gregorian calendar]]).
* Dates before 15{{nbsp}}October 1582 (when the Gregorian calendar was adopted) are normally given in the Julian calendar. The Julian day and month should not be converted to the Gregorian calendar, but the start of the [[Julian year (calendar)|Julian year]] should be assumed to be 1{{nbsp}}January (see below for more details).
* Dates for Roman history before 45{{nbsp}}BC are given in the [[Roman calendar]], which was neither Julian nor Gregorian. When (rarely) the Julian equivalent is certain, it may be included.
* For dates in early Egyptian and Mesopotamian history, Julian or Gregorian equivalents are often uncertain. Follow the consensus of reliable sources, or indicate their divergence.
The dating method used should follow that used by reliable secondary sources (or if reliable sources disagree, that used most commonly, with an explanatory [[WP:FOOT|footnote]]).
At some places and times, the new year began on a date other than 1{{nbsp}}January. For example, in England and its colonies until 1752, the year began on [[Annunciation Day]], 25{{nbsp}}March; see the [[New Year|New Year article]] for other styles. In writing about historical events, however, years should be assumed to have begun on 1{{nbsp}}January (see the example of the execution of Charles I in "[[Old Style and New Style dates#Differences in the start of the year|Differences in the start of the year]]"); if there is reason to use another start-of-year date, this should be noted. 
If there is a need to mention [[Old Style and New Style dates|Old or New Style]] dates in an article (as in the [[Glorious Revolution]]), a footnote should be provided on the first usage, stating whether the ''New Style'' refers to a start of year adjustment or to the Gregorian calendar (it can mean either).
====<span id="Other date ranges"></span><span id="Dates of birth and death"></span>Ranges====
{{shortcut|MOS:DOB|WP:MOSBD|WP:BORN|WP:MOSDOB|WP:OTHERDATE|WP:DATEOTHER|WP:DATERANGE}}
* A pure '''year{{ndash}}year''' range is written (as is any range) using an en dash (<code>&amp;ndash;</code> or <code>{{t|ndash}}</code>), not a hyphen or slash; this dash is usually ''unspaced'' (that is, with no space on either side); and the range's "end" year is usually abbreviated to two digits:
:{{in5|2}}&bull;{{in5|2}} {{xt|1881{{ndash}}86}};{{nbsp}} {{xt|1881{{ndash}}92}} (not {{!xt|1881{{ndash}}6}};{{nbsp}} {{nobr|{{!xt|1881{{snd}}86}}}})
:: {{hanging indent|text=''Markup:'' <code>1881{{t|ndash}}86</code> ''or'' {{nowrap|<code>1881&amp;ndash;86</code>}} }}
: ''But both years are given in full in the following cases:''
:* '''birth{{ndash}}death parentheticals''': {{xt|'''Petrarch''' (1304{{ndash}}1374) was{{nbsp}}...}};{{nbsp}} not {{!xt|(1304{{ndash}}74)}}
:* '''different centuries''': {{xt|1881{{ndash}}1903}};{{nbsp}} not {{!xt|1881{{ndash}}03}}
:* '''starting year before 1000{{nbsp}}AD''': {{xt|355{{ndash}}372}} (not {{!xt|355{{ndash}}72}});{{nbsp}} {{xt|95{{ndash}}113}};{{nbsp}} {{xt|95{{ndash}}113{{nbsp}}AD}};{{nbsp}} {{xt|982{{ndash}}1066}};{{nbsp}} {{xt|2590{{ndash}}2550{{nbsp}}BCE}};{{nbsp}} {{xt|1011{{ndash}}922{{nbsp}}BC}}
:: ''Markup: ''<code>1011{{t|ndash}}922{{t|nbsp}}BC</code>
:* '''spanning from BC/BCE to AD/CE''': {{xt|42{{nbsp}}BC{{snd}}15{{nbsp}}AD}} (note ''spaced'' en dash)
::{{hanging indent|text=''Markup:'' <code>42{{t|nbsp}}BC{{t|snd}}15{{t|nbsp}}AD</code> ''or'' {{nowrap|<code>42&amp;nbsp;BC&amp;nbsp;&amp;ndash; 15&amp;nbsp;AD</code>}} }}
: ''Notes:''
:* Periods straddling two different years, including sports seasons, are generally written with the range notation ({{xt|2005{{ndash}}06}}). The slash notation ({{xt|2005/06}}) may be used to signify a fiscal year or other special period, if that convention is used in reliable sources. 
:*A range of sports seasons in an infobox may also be written as {{xt|2005{{ndash}}2010}}.<ref>{{section link|Wikipedia talk:Manual of Style/Dates and numbers/Archive 144|Date range redux}}</ref>
* Other "pure" ranges use an ''unspaced'' en dash as well:
:* '''day{{ndash}}day''': {{xt|5{{ndash}}7{{nbsp}}January 1979}};{{nbsp}} {{xt|January{{nbsp}}5{{ndash}}7, 1979}};{{nbsp}} {{xt|elections were held March 5{{ndash}}8}}
:* '''month{{ndash}}month''': {{xt|the 1940 peak period was May{{ndash}}July}};{{nbsp}} {{xt|the peak period was May{{ndash}}July 1940}};{{nbsp}} (but {{xt|the peak period was May {{nobr|1940{{snd}}July}} 1940}} uses a ''spaced'' en dash{{mdashb}}see below)
* If ''either or both of the items being linked'' are in a "mixed" format (containing two or more of month, day, year) a ''spaced'' en dash ({{t|snd}}) is used:
:* '''between specific dates in different months''': {{xt|They travelled {{nobr|June{{nbsp}}3{{snd}}August{{nbsp}}18,}} 1952}};{{nbsp}} {{xt|They travelled 3{{nbsp}}June{{snd}}18{{nbsp}}August 1952}} 
:* '''between dates in different years''':
:: {{xt|'''Charles Robert Darwin''' (12{{nbsp}}February {{nobr|1809{{snd}}19{{nbsp}}April}} 1882) was an English naturalist{{nbsp}}...}}
:: {{hanging indent|text=''Markup:'' <code>12{{t|nbsp}}February 1809{{t|snd}}19{{t|nbsp}}April 1882</code> ''or'' {{nowrap|<code>12&amp;nbsp;February 1809&amp;nbsp;&amp;ndash; 19&amp;nbsp;April 1882</code>}} }}
:: {{xt|'''Abraham Lincoln''' (February{{nbsp}}12, 1809{{snd}}April{{nbsp}}15, 1865) was the 16th President of{{nbsp}}...}} 
:* '''between months in different years''': {{xt|The exception was in force August {{nobr|1892{{snd}}January}} 1903}};{{nbsp}} {{xt|The Ghent Incursion (March 1822{{snd}}January{{nbsp}}1, 1823) was ended by the New Year's Treaty}}
::{{hanging indent|text=''Markup:'' <code>March 1822{{t|snd}}January{{t|nbsp}}1, 1823</code> ''or'' {{nowrap|<code>March 1822&amp;nbsp;&amp;ndash; January&amp;nbsp;1, 1823</code>}} }}
* For a person still living: {{xt|'''Serena Williams''' (born September{{nbsp}}26, 1981) is a{{nbsp}}...}}, not {{!xt|(September{{nbsp}}26, 1981{{ndash}})}} or {{!xt|(born on September{{nbsp}}26, 1981)}}
* An overnight period may be expressed using a slash between two contiguous dates: {{xt|the night raids of 30/31{{nbsp}}May 1942}} or {{xt|raids of 31{{nbsp}}May{{nbsp}}/ 1{{nbsp}}June 1942}}.
: Or use an en dash: {{xt|raids of 30{{ndash}}31{{nbsp}}May 1942}};{{nbsp}}  {{xt|raids of {{nobr|31{{nbsp}}May{{snd}}1{{nbsp}}June}} 1942}}. 
* Use a dash, or a word such as ''from'' or ''between'', but not both: {{xt|from 1881 to 1886}} (not {{!xt|{{nobr|from 1881{{ndash}}86}}}});{{nbsp}} {{xt|between June{{nbsp}}1 and July{{nbsp}}3}} (not {{!xt|{{nobr|between June{{nbsp}}1{{snd}}July{{nbsp}}3}}}})
Use [[:ವರ್ಗ:Date mathematics templates|date mathematics templates]] for age calculations in infoboxes and so on; see [[Wikipedia:Manual of Style/Biographies]].
====Uncertain, incomplete, or approximate dates====
* To indicate ''around,'' ''approximately'', or ''about'', the use of the spaced, unitalicised form {{xt|c.{{nbsp}}1291}} (or the {{t|circa}} template) is preferred over {{!xt|circa}}, {{!xt|ca}}, {{!xt|ca.}}, {{!xt|approximately}}, or {{!xt|approx.}}:
:{{in5|2}}&bull;{{in5|2}} {{xt|At the birth of Roger Bacon (c. 1214){{nbsp}}...}}
:{{in5|2}}&bull;{{in5|2}} {{xt|'''John Sayer''' ({{circa}} 1750{{snd}}2{{nbsp}}October 1818){{nbsp}}...}}
:{{in5|2}}&bull;{{in5|2}} {{xt|the Igehalkid dynasty of Elam, {{circa}} 1400{{nbsp}}BC{{nbsp}}...}}
* Where both endpoints of a range are approximate, c. should appear before each date:
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Dionysius Exiguus''' ({{circa}} 470{{snd}}{{circa}} 540){{nbsp}}...}} (not {{!xt|'''Dionysius Exiguus''' ({{circa}} 470{{snd}}540){{nbsp}}...}})
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Rameses III''' (reigned {{circa}} 1180{{snd}}{{circa}} 1150{{nbsp}}BCE){{nbsp}}...}} (not {{!xt|'''Rameses III''' (reigned {{circa}} 1180{{snd}}1150{{nbsp}}BCE){{nbsp}}...}})
* Where birth/death dates have been extrapolated from known dates of activity:
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Offa of Mercia''' (before 734{{snd}}26{{nbsp}}July 796){{nbsp}}...}}
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Robert Menli Lyon''' (1789{{snd}}after 1863){{nbsp}}...}}
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Ambrose Gwinnett Bierce''' (June 24, 1842{{snd}}after December 26, 1913){{nbsp}}...}} <!-- relationship between "before/after" and "fl" needs to be clarified-->
* When a person is known to have been active ("flourishing") during certain years, {{xt|fl.}}, <code><nowiki>[[floruit|fl.]]</nowiki></code>, or {{tl|fl.}} may be used:
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Osmund''' ({{fl.|760&ndash;772}}){{nbsp}}...}}
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Aethelwalh''' ({{fl.|c. 660{{snd}}685}}){{nbsp}}...}}
: The linked forms should not be used on disambiguation pages, and "active" followed by the range is a better alternative for artists, soldiers and other persons with an occupation.<!-- Huh? As opposed to kings, queens, and clergymen, who sit around all day? What about mathematicians -- do they have an "occupation"? -->
* When a date is known to be either of two years (e.g. from a [[Regnal years of English monarchs|regnal]] or [[Hijri year|AH]] year conversion, or a known age at death):
:{{in5|2}}&bull;{{in5|2}} {{xt|'''Anne Smith''' (born 1912 or 1913; died 2013){{nbsp}}...}}
* Other forms of uncertainty should be expressed in words, either in article text or in a footnote: {{xt|April{{nbsp}}14, 1224 (unattested date)}}. Do not use a question mark ({{!xt|1291?}}) for such purposes, as this fails to communicate the nature of the uncertainty.
===<span id="Day, month and season names"></span><span id="Longer periods"></span>Other periods===
====Days of the week====
*Days of the week are capitalized ({{xt|Sunday}}, {{xt|Wednesday}}).
====Months====
{{shortcut|WP:MONTH|MOS:MONTH}}
*Months are normally expressed as capitalized whole words (e.g. {{xt|March}}).
:*Write {{xt|March{{nbsp}}2001}}, not {{!xt|March of 2001}} or {{!xt|March, 2001}}.
:*Three-letter abbreviations such as {{xt|Mar}} should be used only where space is limited, such as in tables and infoboxes. An abbreviated month should not be followed by a period (full stop) except at the end of a sentence.<ref>{{section link|Wikipedia talk:Manual of Style/Archive 151|RFC: Month abbreviations}}</ref>
*Do not express months as numbers ({{!xt|monthly sales peaked in 3/2001}}).
:*An exception is the {{nowrap|{{small caps|YYYY-MM-DD}}}} format e.g. {{xt|{{nowrap|2001-03-05}}}} for March 5, 2001 (but note that this format has restricted use{{mdashb}}see {{section link||Date formats}}).
:*Do not use {{nowrap|{{small caps|YYYY-MM}}}} format, because it can be mistaken for a range of years ({{!xt|{{nowrap|2001-03}}}}, if used to denote March 2001, may be misread as referring to the years {{nobr|2001{{ndash}}2003}}).
====Seasons====
{{shortcut|WP:SEASON|MOS:SEASON}}
*Seasons are uncapitalized ({{xt|a hot summer}}) except when personified: {{xt|Soon Spring will show her colors}}; {{xt|Old Man Winter}}.
*Using seasons to refer to a particular time of year, for example, {{!xt|winter 1995}} is ambiguous. This is because northern and southern hemisphere seasons are six months out of phase, and many areas near the equator instead have [[Wet season|wet]] and [[dry season]]s. 
*Consider instead {{xt|early 1995}};{{nbsp}} {{xt|the first quarter of 1995}};{{nbsp}} {{xt|January to March 1995;}} {{nbsp}} {{xt|spent the southern summer in Antarctica;}}.
*Using seasons is appropriate in instances like these: {{xt|the autumn harvest}};{{nbsp}} {{xt|migration typically begins in mid-spring}}.
====Decades====
{{shortcut|WP:DECADE|MOS:DECADE}}
*To refer to a decade as a chronological period ''per se'' (not with reference to a social era or cultural phenomenon) always use four digits ({{xt|the{{nbsp}}1980s}}, but not {{!xt|the{{nbsp}}1980's}} or {{!xt|the{{nbsp}}1980{{nbh}}ies}}, and ''definitely'' not {{!xt|the{{nbsp}}1980s'}}).
:* Prefixes should be hyphenated ({{xt|the{{nbsp}}mid{{nbh}}1980s}};{{nbsp}} {{xt|pre{{nbh}}1960s social attitudes}}).<!-- nonbreaking hyphens {{nbh}} are used in some examples to keep them from being fragmented over linebreaks here in MOS -- that's not to say nbh ought to be used in "real life" in such situations -->
*For a social era or cultural phenomenon associated with a particular decade:
:*Two digits (with a preceding apostrophe) may be used as an alternative to four digits, ''but only if this is a well-established phrase seen in reliable sources'' ({{xt|the{{nbsp}}Roaring{{nbsp}}'20s}},{{nbsp}} {{xt|the{{nbsp}}Gay{{nbsp}}'90s}},{{nbsp}} {{xt|condemning the '60s counterculture}}, but {{xt|grew up in 1960s Boston, moving to Dallas in{{nbsp}}1971}}, and do not write {{!xt|the{{nbsp}}90's}};{{nbsp}} {{!xt|the{{nbsp}}90s}};{{nbsp}} or {{!xt|the{{nbsp}}90s'}}).
:*A third alternative (where seen in reliable sources) is to spell the decade out, capitalized: {{xt|changing attitudes of the Sixties}}
====<span id="centuries"></span><span id="millennia"></span>Centuries and millennia====
{{shortcut|WP:CENTURY|WP:MILLENNIUM}}
*Treat the 1st century AD as years {{nobr|1{{ndash}}100}}, the 17th century as {{nobr|1601{{ndash}}1700}}, and the second millennium as {{nobr|1001{{ndash}}2000}}; similarly, the 1st century BC/BCE was {{nobr|100{{ndash}}1}} BC/BCE, the 17th century was {{nobr|1700{{ndash}}1601}} BC/BCE, and the second millennium {{nobr|2000{{ndash}}1001}} BC/BCE.
**The ''18th century'' ({{nobr|1701{{ndash}}1800}}) and the ''1700s'' ({{nobr|1700{{ndash}}1799}}) are not the same period.
**When using forms such as {{xt|the 1700s}} ensure there is no ambiguity as to whether e.g. {{nobr|1700{{ndash}}1709}}, or {{nobr|1700{{ndash}}1799}}, is meant.<!-- this needs a little ironing out re "1700s"-->
**Note that the sequence of years runs ''...{{nbsp}}2{{nbsp}}BC, 1{{nbsp}}BC, 1{{nbsp}}AD, 2{{nbsp}}AD{{nbsp}}...''{{mdashb}}there is no "[[Year 0|year 0]]".
* Centuries and millennia are identified using either figures ({{xt|the 18th{{nbsp}}century}}, not {{!xt|XVIII century}}) or words ({{xt|the second millennium}}).<!--actually, I wonder whether "1st millennium" and "2nd millennium" are really appropriate -- they look funny--> When used adjectivally they contain a hyphen ({{xt|nineteenth-century painting}} or {{xt|19th-century painting}}). Do not capitalize ({{!xt|the best Nineteenth-century paintings}};{{nbsp}} {{!xt|during the Nineteenth Century}}).
:*See [[WP:ENDASH]] for use of hyphens and dashes in obscure situations.
====Abbreviations for long periods of time====
*When the term is frequent, combine the abbreviations "yr" for "years" and "ya" for "years ago" with prefixes "k" for "thousand" (kya, kyr), "m" for "million" ([[mya (unit)|mya]], myr), and "b" for "billion" ([[bya]], byr).
*In academic contexts, [[annum]]-based units are often used: "ka" (kiloannum), "Ma" (megaannum) and "Ga" (gigaannum). Some authorities, such as the [[British Museum]], simply spell out "years ago".
*For any of these abbreviations, show the meaning parenthetically on first occurrence and again where use is extensive,{{huh}} or might be a standalone topic of interest.  For source quotations use square brackets, as in {{xt|"a measured Libby radiocarbon date of 35.1{{nbsp}}mya [million years ago] required calibration ..."}}
==Numbers==
===Numbers as figures or words===
{{shortcut|WP:NUMERAL|MOS:NUMERAL|WP:SPELL09|MOS:SPELL09}}
''See also information on specific situations, elsewhere in this guideline.''
Generally, in article text:
* Integers from zero to nine are spelled out in words
* Integers greater than nine ''expressible in one or two words'' may be expressed either in numerals or in words ({{xt|16}} or {{xt|sixteen}}, {{xt|84}} or {{xt|eighty-four}}, {{xt|200}} or {{xt|two hundred}}). In spelling out numbers, "components" from 21 to 99 are hyphenated; larger ones are not ({{xt|fifty-six}}, {{xt|five hundred}}).
* Other numbers are given in numerals ({{xt|3.75}}, {{xt|544}}) or in forms such as {{xt|21{{nbsp}}million}}. ''Markup:'' {{nowrap|<code><nowiki>21{{nbsp}}million</nowiki></code>}}
:* ''billion'' and ''trillion'' are understood to represent their [[Long and short scales|short-scale]] values of 10<sup>9</sup>{{nbsp}}(1,000,000,000) and 10<sup>12</sup>{{nbsp}}(1,000,000,000,000), respectively.
:* ''M'' (unspaced) and ''bn'' (unspaced) may be used for ''million'' and ''billion'' after spelling out the first occurrence (e.g. {{xt|She received &pound;70 million and her son &pound;10M}}).<!--this needs to be coordinated with text in units tables re nonuse of M (for 1000) MM etc-->
:* SI prefixes and symbols, such as ''giga-'' ''(G)'' and ''tera-'' (''T''), should be restricted to use in scientific and engineering expressions.
:*Sometimes, the [[Wikipedia:Manual of Style#National varieties of English|variety of English]] used in an article may call for the use of a numbering system other than the Western thousands-based system. For example, the [[South Asian numbering system]] is convention{{shy}}ally used in [[South Asian English]]. In those situations, link the first spelled-out instance of each quantity (e.g. <code><nowiki>[[crore]]</nowiki></code>, which yields [[crore]]). (If no instances are spelled out, provide a note after the first instance directing the reader to the article about the numbering system.) Also, provide a conversion to Western numbers for the first instance of each quantity, and provide conversions for subsequent instances if they do not overwhelm the content of the article. For example, write {{xt|three [[crore]] (thirty million)}}. Group digits in Western thousands-based style (e.g., {{xt|30,000,000}}; not {{!xt|3,00,00,000}}): see {{section link||Delimiting (grouping of digits)}} below. (Note that the variety of English does not uniquely determine the method of numbering in an article. Other considerations, such as conventions used in mathematics, science and engineering, may also apply, and the choice and order of formats and conversions is a matter of editorial discretion and consensus.)
{{anchor|Numeral notes}}{{shortcut|WP:NUMNOTES}}
Notes and exceptions:
* In tables and infoboxes, quantities are expressed in figures ({{xt|'''Years in office:'''{{nbsp}}5}}); but numbers within a table's explanatory text and comments follow the general rule.
* Numbers in mathematical formulae are never spelled out ({{xt|3{{nbsp}}<{{nbsp}}π{{nbsp}}<{{nbsp}}22/7}}, not {{!xt|three < π < 22 sevenths}}).
* Comparable quantities should be all spelled out or all in figures:
: {{in5|2}}&bull;{{in5|2}}{{xt|five cats and thirty-two dogs}}, not {{!xt|five cats and 32 dogs}}.
: {{in5|2}}&bull;{{in5|2}}{{xt|86{{nbsp}}men and 103{{nbsp}}women}}, not {{!xt|eighty-six men and 103 women}} 
: {{in5|2}}&bull;{{in5|2}}{{xt|There were 3 deaths and 206 injuries}} (even though ''3'' would normally be given as ''three'') or {{xt|Three died and two hundred six were injured}} (even though ''two hundred six'' would normally be given as ''206''), not {{!xt|There were three deaths and 206 injuries}}
* But adjacent quantities not comparable should usually be in ''different formats:'' {{xt|twelve 90-minute volumes}} or {{xt|12 ninety-minute volumes}}, not {{!xt|12 90-minute volumes}} or {{!xt|twelve ninety-minute volumes}}.
:*Avoid awkward juxtapositions: {{xt|On April 28, 2006, thirty-one more died.}}, not {{!xt|On April 28, 2006, 31 more died.}}
* Ages are typically stated in figures ({{xt|8-year-old child}})<!--what is the origin of this provision? should it just say "personal ages..."?--> except for large, approximate values ({{xt|69-million-year-old fossil}}).
* Sometimes figures and words carry different meanings; for example {{xt|Every locker except one was searched}} implies there is a single exception (we don't know which), while {{xt|Every locker except 1 was searched}} means that Locker 1 (only) was not searched.
* Proper names, technical terms, and the like are never altered:
{{xt|''The Sixth Sense''}};{{nbsp}} {{xt|5{{nbsp}}Channel Street}};{{nbsp}} {{xt|Channel{{nbsp}}5}};{{nbsp}} {{xt|Chanel No. 5}};{{nbsp}} {{xt|Fourth Estate}};{{nbsp}} {{xt|Third Reich}};{{nbsp}} {{xt|Second Judicial District}};{{nbsp}} {{xt|First Amendment}};{{nbsp}} {{xt|''Zero Hour''}};{{nbsp}}<!--blast off!-->
* Avoid beginning a sentence with figures:
:{{in5|2}}&bull;{{in5|2}} Not {{!xt|There were many attacks. 23 men were killed}}, but {{xt|There were many attacks; 23{{nbsp}}men were killed}} or {{xt|There were many attacks. Twenty-three men were killed}}.
:{{in5|2}}&bull;{{in5|2}} Not {{nowrap|{{!xt|1945 and 1950 saw crucial elections}}}} (nor {{nowrap|{{!xt|Nineteen forty-five and 1950 saw crucial elections}}}}{{snd}} because comparable numbers should be both written in words or both in figures) but {{nowrap|{{xt|The elections of 1945 and 1950 were crucial.}}}}<!--Examples still need work, and need something about "nineteen forty-five"-type years-->
:*Exception: Where a proper name, technical term, etc., itself beginning with a numeral, opens the sentence ({{xt|1-Naphthylamine is typically synthesized via the Felden{{shy}}shlager{{ndash}}Glocken{{shy}}spiel process}}) although this can usually be avoided by rewording ({{xt|Felden{{shy}}shlager{{ndash}}Glocken{{shy}}spiel is the process typically used in the synthesis of 1-Naphthylamine}}).
{{shortcut|MOS:ORDINAL|WP:ORDINAL}}<!--positioned before (rather than after) section in question to avoid crash of shortcut boxes when sections are short-->
===Ordinals===
* {{anchor|1st}}[[Ordinal numbers (linguistics)|Ordinal]] suffixes (''st'', ''nd'', ''rd'', ''th'') are not [[superscript]]ed ({{xt|123rd}} and {{xt|496th}}, not {{!xt|123<sup>rd</sup>}} nor {{!xt|496<sup>th</sup>}}).
* Do not use a dot ({{!xt|.}}) or the ordinal mark ({{!xt|&#186;}}) to indicate ordinals.
===Fractions===
{{shortcut|MOS:FRAC}}
* Spelled-out fractions are hyphenated: {{xt|seven-eighths}}.
* Where numerator and denominator can each be expressed in one word, a fraction is usually [[Fractions#Pronunciation and spelling|spelled out]] (e.g. {{xt|a two-thirds majority}}); use figures if they occur with an abbreviated unit (e.g. {{xt|{{frac|1|4}}{{nbsp}}yd}}{{mdash}}''markup:'' <code>{{[[Template:frac|frac]]|1|4}}&amp;nbsp;yd</code>, not {{!xt|a quarter of a yd}} or {{!xt|a quarter yd}}).
* [[Mixed numbers]] are usually given in figures, unspaced (not {{!xt|Fellini's film ''8{{nbsp}}{{frac|1|2}}''}} or {{!xt|''8-{{frac|1|2}}''}} but {{xt|Fellini's film ''8{{frac|1|2}}''}}{{mdash}}''markup:'' <code><nowiki>8{{frac|1|2}}</nowiki></code>). In any case the integer and fractional parts should be consistent (not {{!xt|nine and{{nbsp}}{{frac|1|2}}}}).
* Metric (SI) measurements generally use decimals, not fractions ({{xt|5.25{{nbsp}}mm}}, not {{!xt|5{{frac|1|4}}{{nbsp}}mm}}).
* Non-metric (imperial and US customary) measurements may use fractions or decimals ({{xt|5{{frac|1|4}}{{nbsp}}inches}};{{nbsp}}{{xt|5.25{{nbsp}}inches}}); the practice of reliable sources should be followed, and within-article consistency is desirable.
* In science and mathematics articles mixed numbers are rarely used (not {{!xt|1{{frac|1|3}} times the original voltage}}, but {{xt|4/3 the original}}) and use of {{t|frac}} is discouraged in favor of one of these styles:
:{{in5|2}}&bull;{{in5|2}} <math>\textstyle\frac{1}{2}</math>{{nbsp}} ''Markup:'' <code><[[WP:MATH|math]]>\textstyle\frac{1}{2}<nowiki></math></nowiki></code>
:{{in5|2}}&bull;{{in5|2}} {{xt|{{sfrac|2}}}}{{nbsp}} ''Markup:'' <code><nowiki>{{sfrac|2}}</nowiki></code>
:{{in5|2}}&bull;{{in5|2}} {{xt|1/2}}{{nbsp}} ''Markup:'' <code>1/2</code>
* Do not use special characters such as &frac12; (''Markup (deprecated):'' <code>&amp;frac12;</code> or <code>&amp;#189;</code>).  
* [[Ordinal indicator#English|Ordinal suffixes]] such as ''th'' should not be used with fractions expressed in figures (not {{!xt|each US state has 1/50th of the [[United States Senate|Senate's]] votes}}, but {{xt|one-fiftieth of the [[United States Senate|Senate's]] votes}}).
* Nouns following [[Fraction (mathematics)#Simple, common, or vulgar fractions|simple fractions]] are singular ({{xt|He took {{frac|4}} dose}},{{nbsp}} {{xt|net change in score was &minus;{{frac|2}} point}},{{nbsp}} {{xt|{{frac|3|2}} dose}}).
* Nouns following mixed numbers are plural ({{xt|victim knew even 1{{frac|1|2}} doses could be fatal}},{{nbsp}} {{xt|they sailed for 4{{frac|2}} nautical miles}}).
===<span id="Decimal points"></span>Decimals===
{{shortcut|WP:DECIMAL|MOS:DECIMAL}}
* A period/full stop (''never'' a comma) is used as the decimal point ({{xt|6.57}}, not {{!xt|6,57}}).
* The number of decimal places should be consistent within a list or context ({{xt|The response rates were 41.0 and 47.4 percent, respectively}}, not {{!xt|41 and 47.4 percent}}), unless different precisions are actually intended.
* Numbers between −1 and +1 require a leading zero ({{xt|0.02}}, not {{!xt|.02}}); exceptions are sporting performance averages ({{xt|.430 [[batting average]]}}) and commonly used terms such as {{xt|.22{{nbsp}}caliber}}.
* Nouns following a number expressed as a decimal are plural ({{xt|averaging 0.7 years}}).
* Indicate repeating digits with an [[Vinculum (symbol)|overbar]] e.g. {{nowrap|<code><nowiki>14.31{{overline|28}}</nowiki></code>}} gives {{xt|14.31{{overline|28}}}}. (Consider explaining this notation on first use.) Do not write e.g. {{nobr|{{!xt|14.31(28)}}}} because it resembles notations for {{section link||Uncertainty}}.
====<span id="Delimiting (grouping of digits)"></span>Grouping of digits====
* Left of the decimal point: Five or more digits should be grouped (and exactly four digits may ''optionally'' be grouped) into triples separated by commas (''never'' period/full stop): {{xt|12,200}};{{nbsp}}{{nbsp}} {{xt|255,200}};{{nbsp}}{{nbsp}} {{xt|8,274,527}};{{nbsp}}{{nbsp}} {{xt|1,250}} (optionally {{xt|1250}}).
:* Exception: never group four-digit page numbers or four-digit calendar years' (not {{!xt|sailed in 1,492}}, though {{xt|10,400{{nbsp}}BC}}).
:* In scientific/engineering articles, long strings left of the point may be grouped into triples: {{xt|{{gaps|8|274|527}}}}
* Right of the decimal point: Five or more digits may be grouped into triples separated by spaces: {{xt|{{val|99.123456}}}}.
:* In mathematics-oriented articles, digits right of the point may be grouped into fives: {{xt|{{gaps|3.14159|26535|89793|23846|...}}}}.
Delimiting style should be consistent throughout a given article.
''Markup:'' Templates {{t|val}}, {{t|val/delimitnum}} and {{t|gaps}} may be useful in grouping digits. Use of hard-coded spaces, such as the regular space character, the non-breaking space (<code>&amp;nbsp;</code>), and the thin space (<code>&amp;thinsp;</code> or {{t|thinsp}}), is problematic for [[screen reader]]s because they read out each group of digits as separate numbers (e.g. {{xt|30 000}} is read as "thirty zero zero zero").<!--perhaps should say something more re nbsp here since some will hand-code the markup; also, do {{val}} and [[gaps}} use nbsp?  should they? (answer may be different left of the point vs right of the point)-->
===Percentages===
{{shortcut|MOS:PERCENT|WP:PERCENT|WP:%}}
* In the body of non-scientific/non-technical articles, ''percent'' (American English) or ''per cent'' (British English) are commonly used: {{xt|10 percent}}; {{xt|ten percent}}; {{xt|4.5 per cent}}. Ranges are written {{xt|ten to twelve per cent}} or {{xt|ten to twelve percent}}, not {{!xt|ten{{ndash}}twelve per cent}} or {{!xt|ten to twelve %}}.
* In the body of scientific/{{zwsp}}technical articles, and in '''tables and infoboxes''' of any article, the symbol ''%'' (unspaced) is more common: {{xt|71%}}, not {{!xt|71 %}} or {{!xt|three %}}. Ranges: {{xt|10{{ndash}}12%}}, not {{!xt|10%{{ndash}}12%}} or {{!xt|10 to 12%}}.
* When expressing the difference between two percentages, do not confuse a percentage change with a change in [[percentage point]]s.
===<span id="Scientific notation, engineering notation, and uncertainty"></span>Scientific and engineering notation===
* [[Scientific notation]] always has a single nonzero digit to the left of the point: not {{!xt|{{val|60.22|e=22}}}}, but {{xt|{{val|6.022|e=23}}}}. 
* [[Engineering notation]] is similar, but adjusted so that the exponent is a multiple of three: {{xt|{{val|602.2|e=21}}}}.
* Avoid mixing scientific and engineering notations ({{!xt|A {{val|2.23|e=2|u=m2}} region covered by {{val|234.0|e=6|u=grains of sand}}}}). 
* In a table column (or other presentation) in which all values can be expressed with a single power of 10, consider giving e.g. {{xt|&times;&nbsp;10{{sup|7}}}} once in the column header, and omitting it in the individual entries. (''Markup:''<code><nowiki>&amp;times;&amp;nbsp;10{{sup|7}}</nowiki></code>)
* In both notations, the number of digits indicates the precision. For example, {{xt|{{val|5|e=3}}}} means rounded to the nearest thousand; {{xt|{{val|5.0|e=3}}}} to the nearest hundred; {{xt|{{val|5.00|e=3}}}} to the nearest ten; and {{xt|{{val|5.000|e=3}}}} to the nearest unit.
''Markup:'' {{t|Val}} and {{t|e}} may be used to format exponential notation.
===Uncertainty and rounding <span id="Uncertainty"></span> <span id="Large numbers"></span>===
{{shortcut|MOS:UNCERTAINTY|MOS:LARGENUM}}
* Where explicit uncertainty information (such as a "[[margin of error]]") is available and appropriate for inclusion, it may be written in various ways:
:{{in5|2}}&bull;{{in5|2}}{{xt|(1.534 ± 0.035)&thinsp;{{e|23}} m}}{{nbsp}} 
:{{in5|2}}&bull;{{in5|2}}{{xt|12.34{{nbsp}}m<sup>2</sup>{{nbsp}}{{plusmn}}{{nbsp}}5%}} (not used with scientific notation)
:{{in5|2}}&bull;{{in5|2}}{{xt|15.34 {{±|0.43|0.23}} {{e|23}} m}}{{nbsp}} 
:{{in5|2}}&bull;{{in5|2}}{{xt|1.604(48)&thinsp;{{e|-4}} J}} (equivalent to {{val|1.604|0.048|e=-4|u=J}})<ref>The number in parentheses is the numerical value of the standard uncertainty referred to the corresponding last digits of the quoted result – see [http://www.physics.nist.gov/cgi-bin/cuu/Info/Constants/definitions.html NIST – Use of concise notation]</ref>
:{{in5|2}}&bull;{{in5|2}}{{xt|Polls estimated Jones's share of the vote would be 55%, give or take about 3%}}
:''Markup:'' {{t|+-}}, {{t|su}}, and {{t|val}} may be used to format uncertainties.
* Where explicit '''uncertainty is unavailable''' (or is unimportant for the article's purposes) round to an appropriate number of [[significant digit]]s; the precision presented should usually be conservative. Precise values (often given in sources for formal or matter-of-record reasons) should be used only where stable and appropriate to the context, or significant in themselves for some special reason.
:{{in5|2}}&bull;{{in5|2}} {{xt|The speed of light is defined to be 299,792,458{{nbsp}}m/s}}
::''but'' {{xt|Particle velocities eventually reached almost two-thirds the 300{{nbsp}}million m/s speed of light}}
:{{in5|2}}&bull;{{in5|2}} {{xt|The city's 1920 population was 667,000.}} (not {{!xt|population was 666,666}}{{mdashb}}an official figure unlikely to be accurate at full precision)
::''but'' {{xt|The town was ineligible because its official census figure (9,996) fell short of the statutory minimum of ten thousand.}} (Unusual case in which the full-precision official population figure is helpful to readers.)
:{{in5|2}}&bull;{{in5|2}} {{xt| The accident killed 337 passengers and crew, and three airport workers. }} (Likely that accurate and precise figures were determined.)
:{{in5|2}}&bull;{{in5|2}} {{xt| At least 800 persons died in the ensuing mudslides.}} (Unlikely that any precise number can be accurate, even if an official figure is issued.)
::''or'' {{xt| Officials listed 835 deaths, but the Red Cross said dozens more may have gone unreported. }} (In reporting conflicting information, give detail sufficient to make the contrast intelligible.)
:{{in5|2}}&bull;{{in5|2}} {{xt|The jury's award was $8.5{{nbsp}}million}} (where the actual figure was $8,462,247.63){{xt|{{snd}}reduced on appeal to $3,000,001 (one dollar in [[actual damages]], the remainder in [[punitive damages]]).}}
*It may sometimes be appropriate to note the ''lack'' of uncertainty information, especially where such information is normally provided and necessary for full interpretation of the figures supplied.
:{{in5|2}}&bull;{{in5|2}} {{xt|A local newspaper poll predicted 52% of the vote would go to Smith, but did not publish information on the uncertainty of this estimate.}}
*The {{tl|undue precision}} template may be added to figures appearing to be overprecise.
* Avoid using "approximately", "about'' and similar terms with figures that have merely been approximated or rounded in a normal and expected way, unless the reader might otherwise be misled.
:{{in5|2}}&bull;{{in5|2}} {{xt|The tallest player was 6 feet 3 inches}} ({{nobr|not {{!xt|... about 6 feet 3 inches}}}}{{mdashb}}heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle).<!-- please, no lectures about SI -- if you can give a parallel metric example please do so-->
::''but'' {{xt|The man police are seeking is about 5 feet 8 inches tall, with dark hair}}.
* The reader may be assumed to interpret large round numbers ({{xt|100,000 troops}}) as approximations. Writing a quantity in words ({{xt|one hundred thousand troops}}) can further emphasize its approximate nature.
*See {{section link||Unit conversions}} below for precision issues when converting units.
===Non-[[radix|base]]-10 notations===
{{shortcut|MOS:BASE|MOS:RADIX|MOS:BINARY|MOS:HEX}}
* In computer-related articles, use the [[C (programming language)|C programming language]] prefixes <tt>0x</tt> (zero-ex) for hexadecimal and <tt>0</tt> (zero) for octal.  For binary, use <tt>0b</tt>. <!-- Note that 0b is *not* a valid C prefix --> Explain these prefixes in the article's introduction or on first use.
* In all other articles, use <code>&lt;sub></code> to create subscripts: {{xt|137<sub>9</sub>}}, {{xt|241<sub>3</sub>}}. ''Markup:'' {{xt|137<code><nowiki><sub>9</sub></nowiki></code>}}, {{xt|241<code><nowiki><sub>3</sub></nowiki></code>}}
* For bases above 10, use symbols conventional for that base (as seen in reliable sources) e.g. for [[base 16]] use {{nobr|0{{ndash}}9A{{ndash}}F}}.
== Units of measurement ==
{{Shortcut|WP:UNIT|WP:UNITS|WP:METRIC|WP:MEASUREMENT}}
===Choice of units===
Quantities are typically expressed using an appropriate "main" unit, in some cases followed by a conversion to other units in parentheses. For use of such conversions, see {{section link||Unit conversions}} below. 
*In '''most articles, including all scientific articles''', the main units chosen will be [[International System of Units|SI]] units, [[Non-SI units mentioned in the SI|non-SI units officially accepted for use with the SI]], or such other units as are conventional in reliable-source discussions of the article topic (such as [[revolutions per minute]] (rpm) for angular speed, [[hand (unit)|hand]]s for heights of horses, etc.) Example: {{xt|44{{nbsp}}kilograms (97{{nbsp}}lb)}}. The following exceptions apply:
*In '''non-scientific articles relating to the United States''', the main units are [[United States customary units|US customary]], e.g. {{xt|97{{nbsp}}pounds (44{{nbsp}}kg)}}.
*In '''non-scientific articles relating to the United Kingdom''', the main units for most quantities are metric or other internationally used units,<ref name="UKmetricUnits">If there is disagreement about the main units used in a UK-related article, discuss the matter on the article talk-page, at [[WT:MOSNUM|MOSNUM talk]], or both. If consensus cannot be reached, refer to historically stable versions of the article and retain the units used in these as the main units. Note the [[Metrication in the UK#Newspapers|style guides]] of British publications such as ''The Times'' (see [https://web.archive.org/web/20110918050646/http://www.timesonline.co.uk/tol/tools_and_services/specials/style_guide/article986731.ece archived version], under "Metric").</ref> except that:
** the main units for distance/{{zwsp}}length, speed and fuel consumption are miles, miles per hour, and miles per imperial gallon (except for short distances or lengths, where miles are too large for practical use);
** the main units for personal height and weight are feet{{zwsp}}/inches and stones/{{zwsp}}pounds;
** imperial pints are used for quantities of draught beer/{{zwsp}}cider and bottled milk;
** UK engineering-related articles, including all bridges and tunnels, generally use the system of units that the topic was drawn-up in (but road distances are given in imperial units, with a metric conversion).
''Special considerations:''
* Quantities set via definition (as opposed to measured quantities) should be given first in the units used in the definition, even if this makes the structure of presentation inconsistent: {{xt|During metrification, the speed limit was changed from 30{{nbsp}}miles per hour (48{{nbsp}}kilometers/hour) to 50{{nbsp}}km/h (31{{nbsp}}mph)}}.
**This may benefit from a slightly non-standard structure, such as {{xt|...from 30{{nbsp}}miles per hour (about 48{{nbsp}}kilometers/hour) to 50{{nbsp}}km/h (about 31{{nbsp}}mph)}}. In this sort of case, using "about" can help make clear which is the statutory, exact value. 
* Nominal quantities (e.g. {{nowrap|"[[2x4|2 &times; 4]]"}} lumber) require consideration of whether the article is concerned with the item's actual dimensions or merely with its function. In some cases only the nominal quantity may suffice; in others it may be necessary to give the nominal size (often in non-SI units), the actual size in non-SI units, and the actual size in SI units.
* Where the primary units in the article are different from the primary units in the source, ensure that the precision of the converted quantity in the article is comparable to the precision of the quantity from the source (see {{section link||Unit conversions}} below). The {{tl|convert}} template has a <code>|disp=flip</code> flag, which tells it to treat the converted unit as primary and the original unit as secondary, for use in such situations.
===Unit names and symbols===
:''Definitions:''
:*Examples of '''unit names''': foot, meter, kilometer.
:*Examples of '''unit symbols''': ft, m, km.
* Unit names and symbols should follow the practice of reliable sources.
* In prose, unit names should be given in full if used only a few times, but symbols may be used when a unit (especially one with a long name) is used repeatedly, after spelling out the first use (e.g. {{xt|Up to 15{{nbsp}}kilograms of filler is used for a batch of 250{{nbsp}}kg}}).
:*Certain unit names (e.g. {{xt|&deg;C}})<!--<<perhaps identify these in table of specific units elsewhere on this page--> need never be written in full unless required stylistically ({{xt|automatic conversion of degrees Celsius to degrees Fahrenheit}}).
* Where space is limited, such as in tables, infoboxes, parenthetical notes, and mathematical formulas, unit symbols are preferable.
* Units unfamiliar to general readers should be presented as a name{{ndash}}symbol pair ({{xt|Energies were originally 2.3{{nbsp}}[[megaelectronvolt]]s (MeV) initally, but were eventually 6{{nbsp}}MeV}}).
* Ranges use unspaced {{t|ndash}} if only one unit symbol is used at the end (e.g. {{xt|5.9{{ndash}}6.3{{nbsp}}kg}}), and spaced en dash ({{tl|snd}}) if two symbols are used (e.g. {{xt|3{{nbsp}}μm{{snd}}1{{nbsp}}mm}}); ranges in prose may be specified using either unit symbol ''or'' unit names, and units may be stated either after both numerical values or after the last (e.g. {{xt|from 5.9 to 6.3{{nbsp}}kilograms}}, {{xt|from 5.9{{nbsp}}kilograms to 6.3{{nbsp}}kilograms}}, {{xt|from 5.9 to 6.3{{nbsp}}kg}} and {{xt|from 5.9{{nbsp}}kg to 6.3{{nbsp}}kg}} are all acceptable).
* Length{{ndash}}width, length{{ndash}}width{{ndash}}height and similar dimensions may be separated by the multiplication sign ({{xt|[[×]]}}) or the word ''by''.
** With the multiplication sign, each number should be followed by a unit name or symbol (if appropriate):
::{{in5|2}}&bull;{{in5|2}}{{xt|1{{nbsp}}m &times; 3{{nbsp}}m &times; 6{{nbsp}}m}} or {{xt|(1 &times; 3 &times; 6){{nbsp}}m}}, not {{nobr| {{!xt|1 &times; 3 &times; 6 m}} }} or {{nobr| {{!xt|1 &times; 3 &times; 6{{nbsp}}m<sup>3</sup>}} }}
::{{in5|2}}&bull;{{in5|2}}{{xt|a metal plate 1{{nbsp}}ft &times; 3{{nbsp}}ft &times; 0.25{{nbsp}}in}}
::{{in5|2}}&bull;{{in5|2}}{{xt|a railroad [[easement]] 10{{nbsp}}ft &times; 2.5{{nbsp}}mi}} 
:* With ''by'' the unit need be given only once: {{nobr| {{xt|1 by 3 by 6 metres}} }} or {{nobr| {{xt|1 by 3 by 6 m}} }}
:* The unspaced letter {{xt|x}} may be used in common terms such as {{xt|[[4x4]]}}.
{| class="wikitable"
|+ Unit names and symbols—General guidelines
|-
! Aspect
! width="500px"|Guideline
! [[File:Yes check.svg|11px|link=|alt=]] Acceptable
! [[File:X mark.svg|11px|link=|alt=]] Unacceptable
|-
|'''Spelling'''
|The spelling of certain unit names (some of which are listed in {{section link||Specific units}}, below) varies with the [[WP:ENGVAR|variety of English followed by the article]].
|
|
|-
|rowspan=10|'''Format'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Do not spell out numbers before unit ''symbols''{{nbsp}}...
|{{ xt|5{{nbsp}}min}}
|{{!xt|five{{nbsp}}min}}
|-
|...{{nbsp}}but words <u>or</u> numerals may be used with unit ''names''. 
|{{plainlist|
* {{ xt|five minutes}}
* {{ xt|5 minutes}}
}}
|
|-
| Values not accompanied by units are usually given in figures.<!--doing my best to make sense of this -- help gratefully accepted -->
|{{plainlist|
* {{ xt|Set the control to 10.}}
* [[Up to eleven| {{xt|These go to 11}}]].<ref>See [https://www.youtube.com/watch?v=4xgx4k83zzc]<!--try to give a smile now, roc-man!--></ref>
}}
|{{plainlist|
* {{!xt|Set the control to ten.}}
* {{!xt|These go to eleven.}}
}}
|-
|Write unit names and symbols in upright roman type. 
|{{plainlist|
* {{ xt|10{{nbsp}}m        }}
* {{ xt|29{{nbsp}}kilograms}}
}}
|{{plainlist|
* {{!xt|10{{nbsp}}''m''}}
* {{!xt|29{{nbsp}}''kilograms''}}
}}
|-
|Unit ''names'' are given in lower case except: where any word would be capital{{shy}}ized; where otherwise specified in the SI brochure; where otherwise specified in this Manual of Style.{{clarify}}
|{{plainlist|
* {{ xt|He walked several miles.}}
* {{ xt|Miles of trenches were dug.}}
}}
|{{!xt|A Gallon equals 4 Quarts.}}
|-
| Except as listed in the "Specific units" table below, unit ''symbols'' are uncapi{{shy}}tal{{shy}}ized unless they are derived from a proper name, in which case the first letter (of the base unit name, not of any prefix) is capitalized.<ref>This definition is consistent with all units of measure mentioned in the 8th edition of the [[International System of Units|SI brochure]] and with all units of measure catalogued in [[European units of measurement directives|EU directive 80/181/EEC]]</ref>
|{{plainlist|
* {{ xt|8 kg   }}
* {{ xt|100 kPa}}
}}
|{{plainlist|
* {{!xt|8 Kg    }}
* {{!xt|100 kpa }}
}}
|-
|Unit symbols are undotted.
|{{ xt|38 cm }}
|{{!xt|38 cm.}}
|-
|Except as shown in the "Specific units" table below, a space appears between a numeric value and a unit name or symbol.  In the case of unit ''symbols'',<!--<<restriction of nowrap markup to symbols, not full unit names, seems to be implied by earlier text in this guideline--> <code><nowiki>&amp;nbsp;</nowiki></code> (or {{tl|nowrap}}{{px1}}) should be used to prevent linebreak.''
|{{ xt|29{{nbsp}}kg}}<br />''Markup:'' <code>29&amp;nbsp;kg</code><!--<<add examples of degree etc-->
|{{!xt|29kg}}
|-
|To form a value and a unit ''name'' into a compound adjective use a hyphen or hyphens{{nbsp}}...
|{{plainlist|
* {{ xt|a five-day holiday   }}
* {{ xt|a five-cubic-foot box}}
* {{ xt|a 10-centimeter blade}}
}}
|
|-
|... but a non-breaking space (never hyphen) separates a value and unit ''symbol''.
|{{plainlist|
* {{ xt|a blade 10 cm long   }}<!-- what about "a 10 cm bridge" OK?-->
}}
| {{!xt|a 10-cm blade}}
|-
|rowspan=4|'''Plurals'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|SI unit ''names'' are pluralized by adding ''s'' or ''es''...<!--not that it matters much, but I'm having trouble finding an SI unit taking -es -->
|{{ xt|1 ohm}}, {{xt|10 ohms}}<!--what's an example with "es"?-->
|
|-
|... except for these irregular forms.
|{{plainlist|
* {{ xt|1 henry}},   {{ xt|10 henries}}
* {{ xt|1 hertz}},   {{ xt|10 hertz  }}
* {{ xt|1 lux}},     {{ xt|10 lux    }}
* {{ xt|1 siemens}}, {{ xt|10 siemens}}
}}
|{{plainlist|
* {{!xt|10 henrys }}
* {{!xt|10 hertzes}}
* {{!xt|10 luxes  }}
* {{nbsp}}<!--placeholder so lists line up-->
}}
|-
|Some non-SI units have irregular plurals.<!--this is meant to be placeholder which perhaps someone can expand (though foot, feet is the only example I can think of at the moment)-->
|{{plainlist|
* {{ xt|1 foot}}, {{ xt|10 feet}}
* {{ xt|1 stratum}}, {{ xt|10 strata}} (unusual) <!-- rare, but is occasionally used as a measurement unit; can't think of any others, didn't find any in searching -->
}}
|{{plainlist|
* {{!xt|10 foots}}
* {{!xt|10 stratums}}
}}
|-
|Unit ''symbols'' (in any system) are identical in singular and plural.
|{{plainlist|
* {{nobr|{{ xt|grew from 1 in to 2 in      }} }}
* {{nobr|{{ xt|grew from 1 inch to 2 inches}} }}
* {{nobr|{{ xt|grew from one to two inches }} }}
}}
|{{nobr|{{!xt|grew from 1 in to 2 ins     }} }}
|-
|rowspan=5|'''Powers'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Format exponents using <code><nowiki><sup></nowiki></code>, not special characters.
|{{ xt|km<sup>2</sup>}}<br />''Markup:'' <code>km&lt;sup>2&lt;/sup></code>
|{{!xt|km&#178;}}<br />''Markup:'' <code>km&amp;#178;</code>
|-
|Or use ''squared'' or ''cubed'' (''after'' the unit being modified).
|rowspan=2|{{ xt|ten metres per second squared}}
|{{!xt|ten metres per squared second}}
|-
|rowspan=2|For areas or volumes only, ''square'' or ''cubic'' may be used (''before'' the unit being modified).
|{{!xt|ten metres per square second}}
|-
|{{ xt|grams per square centimeter}}
|
|-
|The abbreviations ''sq'' and ''cu'' may be used for US customary and imperial units but not for SI units.
|{{plainlist|
* {{ xt|15{{nbsp}}sq{{nbsp}}mi}}
* {{ xt|3{{nbsp}}cu{{nbsp}}ft }}
}}
|{{plainlist|
* {{!xt|15{{nbsp}}sq{{nbsp}}km}}
* {{!xt|3{{nbsp}}cu{{nbsp}}m  }}
}}
|-
|rowspan=4|'''Products'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Indicate a product of unit ''names'' with either a hyphen or a space.
|{{plainlist|
* {{ xt|foot-pound}}
* {{ xt|foot pound}}
}}
|{{plainlist|
* {{!xt|footpound        }}
* {{!xt|foot&middot;pound}}
}}
|-
|Indicate a product of unit ''symbols'' with <code>&amp;[[middle dot|middot]];</code> or <code>&amp;[[non-breaking space|nbsp]];</code> (''Note:'' {{t|middot}} is not equivalent to <code>&amp;middot;</code>.)
|{{plainlist|1=  <!--  1= is needed because text below contains =  -->
* {{ xt|ms        }} = millisecond
* {{ xt|m&middot;s}} or {{xt|m{{nbsp}}s}} = metre-second. 
}}
|
|-
|''Exception:'' In some topic areas such as power engineer{{shy}}ing, certain products take neither space nor <code>&amp;middot;</code>. Follow the practice of reliable sources in the article's topic area.
|{{plainlist|
*[[watt hour|{{xt|Wh}}]], [[volt ampere|{{xt|VA}}]], [[ampere hour|{{xt|Ah}}]]
*{{xt|kWh}}, {{xt|MVA}}, {{xt|GAh}}
}}
|
|-
|To pluralize a product of unit ''names'', pluralize only the final unit. (Unit ''symbols'' are never pluralized.)
|{{ xt|ten foot-pounds }}
|{{!xt|ten feet-pounds }}
|-
|rowspan=6|'''Ratios<br />Rates<br />Densities'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Indicate a ratio of unit ''names'' with ''per''.
|{{ xt|meter per second}}
|{{!xt|meter/second}}
|-
|rowspan=2|Indicate a ratio of unit ''symbols'' with a slash (followed by either a single symbol or a parenthesized product of symbols{{mdashb}}do not use multiple slashes); or use{{nbsp}}<sup>&minus;1</sup>,{{nbsp}}<sup>&minus;2</sup>, etc.
|{{plainlist|
* {{ xt|metre per second      }}
* {{ xt|m/s                   }}
* {{ xt|m&middot;s<sup>&minus;1</sup>}}
}}
|{{plainlist|
* {{!xt|mps}}
}}
|-
|{{ xt|kg/(m&middot;s)      }}
|{{plainlist|
* {{!xt|kg/m/s       }}
* {{!xt|kg/m&middot;s}}
}}
|-
|To pluralize a ratio of unit ''names'', pluralize only the "numerator" unit. (Unit ''symbols'' are never pluralized.)
|{{plainlist|
* {{ xt|ten newton-metres per second}}
* {{ xt|10 N&middot;m/s             }}
}}
|
|-
|Some of the special forms used in the imperial and US customary systems are shown here{{nbsp}}...
|{{plainlist|1=  <!--  1= is needed because text below contains =  -->
* {{ xt|mph}} = miles per hour
* {{ xt|mpg}} = miles per gallon
* {{ xt|psi}} = pounds per square inch
}}
|
|-
|... but only the slash or negative exponent notations are used with SI (and other metric) units.
|{{plainlist|
* {{ xt|g/m<sup>2</sup>              }}
* {{ xt|g&middot;m<sup>&minus;2</sup>}}
* {{ xt|km/h                         }}
* {{ xt|km&middot;h<sup>-1</sup>     }}
}}
|{{plainlist|
* {{!xt|gsm}}
* {{!xt|kph}}
}}
|-
|rowspan=4|'''Prefixes'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Prefixes should not be separated by a space or hyphen.
|{{ xt|25 kilopascals}}
|{{plainlist|
* {{!xt|25 kilo pascals}}
* {{!xt|25 kilo-pascals}}
}}
|-
|Prefixes are added without contraction,<!--give example--> except as shown here:
|{{plainlist|
* {{ xt|kilohm }}
* {{ xt|megohm }}
* {{ xt|hectare}}
}}
|{{plainlist|
* {{!xt|kiloohm}}
* {{!xt|megaohm}}
* {{!xt|hectoare}}
}}
|-
|''centi-'', ''deci-'', ''deca-'', and ''hecto-'' should be avoided; exceptions include<!--check SI source; also, since we're supposed to follow the units in sources, don't those control anyway?--> ''centimetre, decibel, hectolitre, hectare, hectopascal''.
|{{plainlist|
* {{ xt|100 metres}}
* {{ xt|0.1 km}}
}}
|{{!xt|1 hectometre}}
|-
|Do not use ''{{!xt|[[wikt:M#Number|M]]}}'' for 10<sup>3</sup>, ''MM'' for 10<sup>6</sup>, or ''B'' for 10<sup>9</sup>.<!-- what about e.g. "deficit of $10B"; MCM = kcmil; etc-->
|{{plainlist|
* {{ xt|3 km   }}
* {{ xt|8 MW   }}
* {{ xt|125 GeV}}
}}
|{{plainlist|
* {{!xt|3 Mm   }}
* {{!xt|8 MMW  }}
* {{!xt|125 BeV}}
}}
|-
|rowspan=4|'''Mixed<br />units'''<!--<< <br /> to make this column as narrow as possible--><!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF RULES - - - -->
|Mixed units are traditionally used with the imperial and US customary systems{{nbsp}}…
|{{anchor|mixed units}}<!--<<this anchor should go at the portion of the row which is vertically highest-->{{plainlist|
* {{ xt|1 ft 6 in      }}
* {{ xt|1 foot 6 inches}}
* {{ xt|1.5 ft         }}
* {{ xt|18 in          }}
* {{ xt|1 US fl pt 8 oz}}
}}
|
|-
|... and in expressing time durations{{nbsp}}...
|{{plainlist|
* {{ xt|1:30:07}}
* {{ xt|1:30}}{{thinsp}}<ref group=upper-alpha>Only use this format if it is clear from the context whether this means hours and minutes (H:MM) or minutes and seconds (M:SS).</ref>
* {{ xt|{{nobr|1 hr 30 min 7 sec}}}}
* {{ xt|{{nobr|1 h 30 m 7 s     }}}}
* {{ xt|{{nobr|1<sup>h </sup>30<sup>m </sup>07<sup>s</sup>}}}}
}}
||{{plainlist|
* {{!xt|{{nobr|1 h 30 min 7 s      }}}}
* {{!xt|{{nobr|1 hr 30 m 7 sec     }}}}
* {{!xt|{{nobr|1:30&prime;07&Prime;}}}}
}}
|-
|… but are not normally used in SI.
|{{plainlist|
* {{ xt|1.33 m  }}
* {{ xt|133 cm  }}
}}
|{{!xt|1 m 33 cm}}
|-
|No comma.
|{{ xt|6 lb 3 oz}}
|{{!xt|6 lb, 3 oz}}
|}
''Note to table:''
{{reflist | group=upper-alpha|close=1}}
===Specific units===
* The following table lists only units that need special attention.
* The [http://www.bipm.org/en/si/ SI standard] should be consulted for guidance on use of other SI units. [http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html "Tables 6, 7, 8, and 9"] give additional guidance on non-SI units.
{|class="wikitable"
|+ Guidelines on specific units
|-
! width="79px" | Group
! width="160px" | Name
! width="140px" | Symbol
! Comment
|-
| rowspan = 10 | '''Length,'''<br />'''Speed'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| inch
| {{ xt|in}}
| rowspan=2|Do not use <code>&amp;prime;</code> ({{!xt|&prime;}}), <code>&amp;Prime;</code> ({{!xt|&Prime;}}), apostrophe/{{zwsp}}single quote ({{!xt|<code>'</code>}}) or double quote ({{!xt|<code>"</code>}})
|-
| foot
| {{ xt|ft}}
|-
| foot per second
| {{ xt|ft/s}} (''not'' {{!xt|fps}})
|
|-
| [[Hand (unit)|hand]]
| {{ xt|h}} ''or'' {{ xt|hh}}
| Equal to 4 inches; used in measurement of horses. A dot may be followed by additional inches e.g. ''16.2 hh'' indicates 16 hands 2 inches.
|-
| knot
| {{ xt|kn}} (''not'' {{!xt| [[kilotonne|kt]]}} ''or'' {{!xt|[[kilonewton|kN]]}})<!--not sure how to resolve the conflicting coloration desiderata-->
|
|-
| {{plainlist|
* metre
* meter ''(U.S.)''
}}
| {{ xt|m}}
|
|-
| micron
| {{ xt|&mu;m}} (''not'' {{!xt|&mu;}})
| ''Markup:'' <code>&amp;mu;m</code>{{nbsp}} Link to [[micrometre]] (for which micron is a synonym) on first use.
|-
| mile
| {{ xt|mi}}
|rowspan=3 | In nautical and aeronautical contexts use {{xt|statute mile}}<!--<<should this be an entry in the table?--> rather than mile to avoid confusion with nautical mile.
|-
| mile per hour
| {{ xt|mph}}<!-- not ever mi/hr??-->
|-
| nautical mile
| {{ xt|nmi}} ''or'' {{xt|NM}} {{nobr|(''not'' {{!xt|[[nanometer|nm]]}})}}
|-
| rowspan = 13 | '''Volume,'''<br />'''Flow'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| rowspan = 2 | {{plainlist|
* cubic centimetre
* cubic centimeter ''(U.S.)''
}}
| {{ xt|cm<sup>3</sup>}}
| ''Markup:'' <code><nowiki>cm<sup>3</sup></nowiki></code>
|-
| {{ xt|cc}}
| Non-SI symbol used for certain [[engine displacement]]s; link to [[cubic centimetre]] on first use.<!-- I wonder if this can't be better coordinated with mpg, mph etc in earlier table-->
|-
| imperial fluid ounce
| {{ xt|imp fl oz}}
| rowspan=8 | ''US'' or ''imperial/imp'' must be specified; ''fluid/fl'' must be specified, except with{{nbsp}}''gallon''. (Without ''fluid'', [[ounce]] is ambiguous{{snd}}versus avoirdupois ounce or troy ounce{{snd}}and [[pint]] or [[quart]] is ambiguous{{snd}}versus US dry pint or US dry quart.)<!--<<Actually, I don't think //imperial fluid quart// or //imperial fluid pint// are correct -- from what I can see it's //imperial quart//, //imperial pint//, there being no imperial "dry" pints of quarts from which these need to be distinguished-->
|-
| imperial fluid pint
| {{ xt|imp fl pt}}
|-
| imperial fluid quart
| {{ xt|imp fl qt}}
|-
| imperial gallon
| {{ xt|imp gal}}
|-
| US fluid ounce
| {{ xt|US fl oz}}
|-
| US fluid pint
| {{ xt|US fl pt}}
|-
| US fluid quart
| {{ xt|US fl qt}}
|-
| US gallon
| {{ xt|US gal}}
|-
| cubic foot
| {{ xt|cu ft}} (''not'' {{!xt|cf}})
| Write {{xt|five million cu ft}} or {{xt|5,000,000{{nbsp}}cu{{nbsp}}ft}}, not {{!xt|5{{nbsp}}MCF}}.
|-
| cubic foot per second
| {{ xt|cu ft/s}} (''not'' {{!xt|cfs}})
|
|-
| {{plainlist|
* litre
* liter ''(U.S.)''
}}
| {{ xt|l}} ''or'' {{xt|L}}
| The symbol l in isolation (i.e. not in such forms as ml) is easily mistaken for the digit 1.
|-
| rowspan=7 | '''Mass,'''<br />'''Force,'''<br />'''Density,'''<br />'''Pressure'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| long ton
| {{ xt|long ton}}
| rowspan=2 | Spell out in full.
|-
| short ton
| {{ xt|short ton}}
|-
| pound per square inch
| {{ xt|psi}}
|
|-
| {{plainlist|
* tonne
* metric ton ''(U.S.)''
}}
| {{ xt|t}} {{nobr|(''not'' {{!xt|mt}} ''or'' {{!xt|MT}})}}
|
|-
| troy ounce
| {{ xt|oz t}}
| rowspan=2 | ''t'' or ''troy'' must be specified. Articles about precious metals, black powder, and gemstones<!--is this list complete--> should always specify whether ounces and pounds are [[Avoirdupois|avoirdupois]] or [[Troy weight|troy]].
|-
| troy pound
| {{ xt|lb t}} or {{ xt|troy}} <!-- source: http://www.weightconversions.org/ -->
|-
| [[Carat (mass)|carat]]
| {{ xt|carat}}
| Used to express masses of gemstones and pearls.
|-
| '''Purity'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| [[Carat (purity)|carat ''or'' karat]]
| {{ xt|k}} ''or'' {{xt|Kt}}
| A measure of purity for gold alloys. (Do not confuse with the unit of mass with the same spelling.)
|-
| rowspan=5 | '''Time'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| second
| {{ xt|s}}
|rowspan=3|Do not use <code>&amp;prime;</code> ({{!xt|&prime;}}), <code>&amp;Prime;</code> ({{!xt|&Prime;}}), apostrophe ({{!xt|<code>'</code>}}) or quote ({{!xt|<code>"</code>}}) for minutes or seconds. Use ''m'' for ''minute'' only where there is no danger of confusion with ''meter'', as in the hours{{ndash}}minutes{{ndash}}seconds formats for time durations described in the [[#Mixed units|Unit names and symbols table]].
|-
| minute
| {{ xt|min}}
|-
| hour
| {{ xt|h}}
|-
| rowspan=2|year
| {{ xt|a}}
| Use ''a'' only with an SI prefix ({{xt|a rock formation 540{{nbsp}}Ma{{nbsp}}old}},<!--<<perhaps this should be explained--> not {{!xt|Life expectancy rose to 60 a}}).
|-
| {{ xt|y}} ''or'' {{xt|yr}}
|
|-
| rowspan=4 |
<small>'''Information'''</small><!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| bit
| {{ xt|bit}} {{nobr|(''not'' {{!xt|b}} ''or'' {{!xt|B}})}}
| rowspan=4 | ''See also {{section link||Quantities of bytes and bits}}, below.''
|-
| byte
| {{ xt|B}} ''or'' {{xt|byte}} {{nobr|(''not'' {{!xt|b}} ''or'' {{!xt|[[octet (computing)|o]]}})}}
|-
| bit per second
| {{ xt|bit/s}} (''not'' {{!xt|bps}})
|-
| byte per second
| {{ xt|B/s}} ''or'' {{xt|byte/s}} {{nobr|(''not'' {{!xt|Bps}} ''or'' {{!xt|Bps}})}}
|-
| rowspan = 4 | '''Angle'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
|-
| [[arcminute]]
| {{ xt|[[prime (symbol)|&prime;]]}}
| ''Markup:'' <code>&amp;prime;</code>{{nbsp}} (not apostrophe/{{zwsp}}single quote{{nbsp}}{{!xt|'}}). No space between numerals and symbol {{nobr|({{xt|47&prime;}}, not {{!xt|47{{nbsp}}&prime;}})}}
|-
| [[arcsecond]]
| {{ xt|[[double prime (symbol)|&Prime;]]}}
| ''Markup:'' <code>&amp;Prime;</code>{{nbsp}} (not double-quote{{nbsp}}{{!xt|"}}). No space between numerals and symbol {{nobr|({{xt|22&Prime;}}, not {{!xt|22{{nbsp}}&Prime;}})}}
|-
| degree
| rowspan=2|{{xt|&deg;}}
| ''Markup:'' <code>&amp;deg;</code>{{nbsp}} (not [[masculine ordinal]] {{!xt|&#186;}} or [[ring (diacritic)|ring]] {{!xt|&#778;}}{{thinsp}}<!--<<thinsp is needed to prevent crash between ring and closing paren, at least on some browsers-->). No space between numerals and symbol {{nobr|({{xt|23&deg;}}, not {{!xt|23{{nbsp}}&deg;}})}}
|-
| rowspan = 2 |
<small>'''Temperature'''</small><!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| degree
| rowspan = 2 | ''Markup:'' <code>&amp;deg;</code>. Nonbreaking space (<code>{{tl|nbsp}}</code>) between numerals and symbol {{nobr|({{xt|40{{nbsp}}&deg;}}, not {{!xt|40&deg;}};}} {{nobr|{{xt|12{{nbsp}}&deg;C}}, not {{!xt|12&deg;C}}, nor {{!xt|12&deg;{{nbsp}}C}})}}
|-
| degree Celsius {{nobr|(''not'' degree centigrade)}}
| {{ xt|&deg;C}} (''not'' {{!xt|C}})
|-
| rowspan = 2 | '''Energy'''<!-- - - - WARNING! ADJUST ROWSPAN WHEN ADDING/REMOVING ROWS FROM A GROUP OF UNITS - - - -->
| {{plainlist|
* [[gram calorie]]
* small calorie
}}
| {{ xt|cal}}
| rowspan=2 | In certain subject areas ''calorie'' is convention{{shy}}ally used alone. Articles following this practice should specify either gram calorie (or small calorie) or kilogram calorie (or large calorie) on first use; providing conversions to SI units  (usually gram calories to joules and kilogram calories to kilojoules) may also be useful. A kilogram calorie is 1000 gram calories, and is therefore also a kilocalorie ({{xt|kcal}}); other SI prefixes may be used with the gram calorie (e.g., {{xt|Mcal}}) but not with the kilogram calorie (do not use {{!xt|kCal}} or {{!xt|MCal}}). 
|-
| {{plainlist|
* [[kilogram calorie]]
* large calorie
* {{nobr|(''not'' Calorie)}}
}}
| {{ xt|Cal}}
|}
====Quantities of bytes and bits <span id="Binary prefixes"></span>====
{{shortcut|WP:COMPUNITS}}
In quantities of [[bit (computing)|bit]]s and [[byte]]s, the prefixes ''kilo'' (symbol k or K), ''mega'' (M), ''giga'' (G), ''tera'' (T), etc. are ambiguous. They may be based on a decimal system (like the standard [[International System of Units|SI]] prefixes), meaning 10<sup>3</sup>, 10<sup>6</sup>, 10<sup>9</sup>, 10<sup>12</sup>, etc., or they may be based on a binary system, meaning 2<sup>10</sup>, 2<sup>20</sup>, 2<sup>30</sup>, 2<sup>40</sup>, etc. The binary meanings are more commonly used in relation to solid-state memory (such as [[Random-access memory|RAM]]), while the decimal meanings are more common for data transmission rates, disk storage and in theoretical calculations in modern academic textbooks.
{{Bit and byte prefixes}}
Follow these recommendations when using these prefixes in Wikipedia articles:
* Following the SI standard, a lower-case {{xt|k}} should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital {{xt|K}} should be used instead to indicate the binary prefix for 1024 according to JEDEC. (If, under the exceptions detailed further below, the article otherwise uses IEC prefixes for binary units, use {{xt|Ki}} instead).
* Do not assume that the binary or decimal meaning of prefixes will be obvious to everyone. Explicitly specify the meaning of k and K as well as the primary meaning of M, G, T, etc. in an article ({{tl|BDprefix}} is a convenient helper). Consistency within each article is desirable, but the need for consistency may be balanced with other considerations.
* The definition most relevant to the article should be chosen as primary for that article, e.g. specify a binary definition in an article on RAM, decimal definition in an article on [[hard drives]], [[bit rate]]s, and a binary definition for Windows file sizes, despite files usually being stored on hard drives.
* Where consistency is not possible, specify wherever there is a deviation from the primary definition.
* Disambiguation should be shown in bytes or bits, with clear indication of whether in binary or decimal base. There is no preference in the way to indicate the number of bytes and bits, but the notation style should be consistent within an article. Acceptable examples include:
:{{in5|2}}&bull;{{in5|2}}{{xt|A 64{{nbsp}}MB ({{nowrap|64 &times; 1024<sup>2</sup>-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100 &times; 1000<sup>3</sup>-byte)}} hard drive}}
:{{in5|2}}&bull;{{in5|2}}{{xt|A 64{{nbsp}}MB ({{nowrap|64 &times; 2<sup>20</sup>-byte)}} video card and a 100{{nbsp}}GB {{nowrap|(100 &times; 10<sup>9</sup>-byte)}} hard drive}}
:{{in5|2}}&bull;{{in5|2}}{{xt|A 64{{nbsp}}MB (67,108,864-byte) video card and a 100{{nbsp}}GB (100,000,000,000-byte) hard drive}}
* Avoid inconsistent combinations such as {{!xt|A 64{{nbsp}}MB (67,108,864-byte) video card and a 100{{nbsp}}GB {{nowrap|(100 &times; 1000<sup>3</sup>-byte)}} hard drive}}. Footnotes, such as those seen in [//en.wikipedia.org/w/index.php?title=Power_Macintosh_5500&oldid=218088888 {{nowrap|Power Macintosh 5500}}], may be used for disambiguation.
* Unless explicitly stated otherwise, one byte is eight bits (see [[Byte#History|History of ''byte'']]).
The [[IEC prefix]]es ''kibi-'', ''mebi-'', ''gibi-'', etc. (symbols Ki, Mi, Gi, etc.) are rarely used, even in technical articles, so are generally not to be used except:<ref>Wikipedia follows common practice regarding [[byte]]s and other data traditionally quantified using [[binary prefix]]es (e.g. mega- and kilo-, meaning 2<sup>20</sup> and 2<sup>10</sup> respectively) and their unit symbols (e.g. MB and KB) for RAM and [[decimal prefix]]es for most other uses.  Despite the IEC's 1998 International Standard creating several new binary prefixes (e.g. mebi-, kibi-) to distinguish the meaning of the decimal [[SI prefix]]es (e.g. mega- and kilo-, meaning 10<sup>6</sup> and 10<sup>3</sup> respectively) from the binary ones, and the subsequent incorporation of these IEC prefixes into the [[IEC 80000-13|International System of Quantities]] (ISQ), consensus on Wikipedia in computing-related contexts currently favours the retention of the more familiar but ambiguous units "KB", "MB", "GB", "TB", "PB", "EB", etc. over use of unambiguous IEC binary prefixes. For detailed discussion, see [[Wikipedia talk:Manual of Style (dates and numbers)/Archive/Complete rewrite of Units of Measurements (June 2008)|Complete rewrite of Units of Measurements (June 2008)]].</ref>
* when the majority of cited sources on the article topic use IEC prefixes,
* in a direct quote using the IEC prefixes,
* when explicitly discussing the IEC prefixes,
* in articles in which both types of prefix are used with neither clearly primary, or in which converting all quantities to one or the other type would be misleading or lose necessary precision, or declaring the actual meaning of a unit on each use would be impractical.
===Unit conversions===
{{shortcut|MOS:CONVERSIONS|WP:MOSCONVERSIONS}}
Where English-speaking countries use different units for the same quantity, follow the "primary" quantity with a conversion in parentheses: {{xt|the Mississippi River is {{convert|2320|mi|km|0}} long}}; {{xt|the Murray River is {{convert|2375|km|mi|0}} long}}. In science-related articles, however, supplying such conversion is not required unless there is some special reason to do so.
* Where an [[imperial unit]] is not part of the [[United States customary units|US customary system]], or vice-versa{{mdashb}}and in particular, where those systems give a single term different definitions{{mdashb}}a double conversion may be appropriate: {{xt|Rosie weighed {{convert|19|st|0}}}}, {{xt|The car had a fuel economy of {{convert|5|L/100km|mpgus mpgimp|abbr=on}}}}
* Generally, conversions to and from metric units and US or imperial units should be provided, except:
** When inserting a conversion would make a common or linked expression awkward ({{xt|The four-minute mile}}).
** When units are part of the subject of a topic{{mdashb}}nautical miles in articles about the history of nautical law ({{xt|5 nautical miles}}), SI units in scientific articles ({{xt|a 600-kilometer asteroid}}), yards in articles about American football{{mdashb}}it can be excessive to provide conversions every time a unit occurs. It could be best to note that this topic will use the units (possibly giving the conversion factor to another familiar unit in a parenthetical note or a footnote), and link the first occurrence of each unit but not give a conversion every time it occurs.
* Converted quantity values should use a level of '''precision''' similar to that of the source quantity value, so {{xt|the Moon is 380,000{{nbsp}}kilometres (240,000{{nbsp}}mi) from Earth}}, not {{!xt|(236,121{{nbsp}}mi)}}. Small numbers may need to be converted to a range where rounding would cause a significant distortion, so {{xt|one mile (1–2{{nbsp}}km)}}, not {{!xt|one mile (2{{nbsp}}km)}}.  Be careful especially when your source has already converted from the units you're now converting back to.  This may be evidenced by multiples of common conversion factors in the data, such as 160 km (from 100 miles). See [[false precision]].
* [[:ವರ್ಗ:Conversion templates|'''Conversion templates''']] can be used to convert and format many common units, including {{t1|convert}}, which includes non-breaking spaces.
* In a '''direct quotation''', always retain the source units. Any conversions can be supplied either in the quote itself (in square brackets, following the original measurement) or in a footnote. See [[Wikipedia:Footnotes|footnoting]] and [[Wikipedia:Citing sources|citing sources]].
* {{t|Units attention}} may be added to articles needing general attention regarding choice of units and unit conversions.
==<span id="Currencies"></span> Currencies and monetary values==
{{shortcut|WP:$|WP:&pound;|WP:€|MOS:CURRENCY}}
{{see also|Wikipedia:WikiProject Numismatics/Style#Article titles}}
===Choice of currency===
* In '''country-specific articles''', such as [[Economy of Australia]], use the currency of the subject country.
* In '''non-country-specific articles''' such as [[Wealth]], use US dollars ({{xt|$123}}), euros ({{xt|&euro;123}}), or pounds sterling ({{xt|&pound;123}}).
===Currency names===
* Do not capitalize the names of currencies, currency subdivisions, coins and banknotes except e.g. at the start of a sentence.<!--It's a bit more complicated than this -- clearly "Australain dollar" uses a capital on Austrailian"-->
* To pluralize ''euro'' use the standard English plurals ({{xt|ten euros and fifty cents}}), not the [[Linguistic issues concerning the euro#English|invariant plurals used for European Union legislation and banknotes]] ({{!xt| ten euro and fifty cent}}). For the adjectival form, use a hyphenated singular: ({{xt|a two-euro pen}};{{nbsp}}{{nbsp}} {{xt|a ten-cent coin}}). 
* Link the first occurrence of lesser-known currencies ({{xt|[[Mongolian tögrög]]s}}).<!--should a symbol be introduced at this time?-->
 
===Currency symbols===<!--symbols? signifiers? abbreviations? see [[ISO 4217]] and [[currency symbol]]s-->
* In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. {{xt|A$52}}), with subsequent references using just the appropriate symbol (e.g. {{xt|$88}}), unless this would be unclear. ''Exceptions:''
:*In an article referring to multiple currencies represented by the same symbol (e.g. the dollars of the US, Canada, Australia, New Zealand, and other countries{{snd}}see {{section link|Currency symbols|dollar variants}}) use the full signifier (e.g. {{xt|US$}}, {{xt|A$}}) each time, except (possibly) where a particular context makes this both unnecessary and undesirable.
:*In articles entirely on EU-, UK- and/or US-related topics, all occurrences may be shortened ({{xt|&euro;26}}, {{xt|&pound;22}} or {{xt|$34}}), unless this would be unclear.
* The [[pound sterling]] is represented by the {{xt|&pound;}} symbol, with one horizontal bar. The double-barred {{!xt|&#8356;}} symbol is ambiguous, as it has also been used for the [[Italian lira]] and other currencies. For non-British currencies that use pounds or a pound symbol (e.g. the [[Irish pound]], IR&pound;) use the symbol convention{{shy}}ally preferred for that currency.<!--If no modern currency still uses the ₤ symbol, the developers should be asked to remove it from the edit tool box to prevent its misuse.-->
* If there is no common English abbreviation or symbol, follow the [[ISO 4217]] standard. See also [[List of circulating currencies]].
===Format===
* A period (full stop) is used as the decimal point{{mdashb}}never a comma ({{xt|$6.57}}, not {{!xt|$6,57}}).
* For the grouping of digits (e.g. {{xt|&pound;1,234,567}}) see {{section link||Grouping of digits}}, above.
* Do not place a currency symbol ''after'' the accompanying numeric figures (e.g. {{!xt|123$}}, {{!xt|123&pound;}}, {{!xt|123&euro;}}) unless that is the normal convention for that currency when writing in English.{{clarify|reason=please give an example}} Never use forms such as {{!xt|$US123}} or {{!xt|$123 (US)}}.
* Currency abbreviations that come before the numeric value are ''unspaced'' if they consist of a nonalphabetic symbol only, or end in a symbol ({{xt|&pound;123}};{{nbsp}}{{nbsp}} {{xt|&euro;123}}); but ''spaced'' if alphabetic ({{xt|R{{nbsp}}75}}).
* Ranges should be expressed giving the currency signifier just once: {{xt|$250&ndash;300}}, not {{!xt|$250&ndash;$300}}.
* ''million'' and ''billion'' should be spelled out on first use, and (optionally) abbreviated ''M'' or ''bn'' (both unspaced) thereafter: {{xt|She received &pound;70 million and her son &pound;10M}}; {{xt|the school's share was $250&ndash;300 million, and the charity's $400&ndash;450M}}.
* In general, a currency symbol should be accompanied by a numeric amount e.g. not {{!xt|He converted his US$ to A$}} but {{xt|He converted his US dollars to Australian dollars}} or {{xt|He exchanged the US$100 note for Australian dollars}}.
:*Exceptions may occur in tables and infoboxes where space is limited e.g. {{xt|''Currencies accepted for deposit:'' [[United States dollar|US$]], [[Swiss franc|SFr]], [[British pound|GB&pound;]], [[Euro|&euro;]]}}. It may be appropriate to wikilink such uses, or add an explanatory note.
===Conversions===
* Conversions of '''less-familiar currencies''' may be provided in terms of more familiar currencies{{mdashb}}such as the US dollar, euro or pound sterling{{mdashb}}using an appropriate rate (which is often ''not'' the current exchange rate). Conversions should be in parentheses after the original currency, rounding to avoid [[false precision]] (two significant digits is usually sufficient, as most exchange rates fluctuate significantly), with at least the year given as a rough point of conversion rate reference; e.g. {{xt|Since 2001 the grant has been 10,000,000 [[Swedish krona|Swedish kronor]] ($1.4M, &euro;1.0M, or &pound;800k {{as of|2009|08|lc=on}})}}, not {{!xt|($1,390,570, &euro;971,673 or &pound;848,646)}}.<!-- is "800k" really acceptable?-->
* For '''obsolete currencies''', provide an equivalent (formatted as a conversion) if possible, in the modern replacement currency (e.g. decimal pounds for historical pre-decimal pounds-and-shillings), or a US-dollar equivalent where there is no modern equivalent.
* In some cases it may be appropriate to provide a conversion accounting for inflation or deflation over time. See {{t|Inflation}} and {{t|Inflation-fn}}.
==<span id="Minus sign"></span>Common mathematical symbols==
{{shortcut|WP:COMMONMATH||MOS:MINUS}}
{{See also|Wikipedia:Manual of Style/Mathematics}}
*This is not an complete list of symbols that may be used.
* Spaces are placed to left and right when a symbol is used with {{nobr|[[binary operation|two operands]]}}, but no space with {{nobr|[[unary operation |one operand]]}}
* The {{t|nbsp}} and {{t|nowrap}} templates may be useful in preventing awkward linebreaks in mathematical material.
{{clear right}}
{|class="wikitable" style="align: center; text-align: center;"
|+Common mathematical symbols
|-
! width=110|Symbol name
! width= 80|Example
! width=335|Markup
! Comments
|-
| rowspan=2| [[Plus sign|Plus /<br />positive]]
| ''x'' + ''y''
| <code><nowiki>''x'' + ''y''</nowiki></code>
| rowspan=2|
|-
| +''y''
| <code><nowiki>+''y''</nowiki></code>
|-
| rowspan=2|[[Minus sign|Minus /<br />negative]]
| ''x'' &minus; ''y''
| <code><nowiki>''x'' &amp;minus; ''y''</nowiki></code>
| rowspan=2|Do not use hyphen ({{!xt|<code>-</code>}}) or dashes ({{!xt|{{t|ndash}}}} {{nobr|or {{!xt|{{t|mdash}}}}).}}
|-
| &minus;''y''
| <code><nowiki>&amp;minus;''y''</nowiki></code>
|-
|  rowspan=2| [[Plus-minus sign|Plus-minus /<br />minus-plus]]
| 41.5 &plusmn; 0.3
| <code><nowiki>41.5 &amp;plusmn; 0.3</nowiki></code>
| rowspan=2|
|-
| &minus;(&plusmn;''a'') = &#8723;''a''
| <code><nowiki>&amp;minus;(&amp;plusmn;''a'') = &amp;#8723;''a''</nowiki></code>
|-
| [[Multiplication sign|Multiplication]],<br />cross
| ''x'' &times; ''y''
| <code><nowiki>''x'' &amp;times; ''y''</nowiki></code> 
| Do not use the letter "x" to indicate multiplication. However, an unspaced "x" may be used as a substitute for "by" in common terms such as "[[4x4]]". 
|-
| [[Division sign|Division]], obelus
| ''x'' &divide; ''y''
| <code><nowiki>''x'' &amp;divide; ''y''</nowiki></code>
| rowspan=8|
|-
| [[Equal sign|Equal / equals]]
| ''x'' = ''y''
| <code><nowiki>''x'' = ''y''</nowiki></code>
|-
| [[Not equal sign|Not equal]]
| ''x'' &ne; ''y''
| <code><nowiki>''x'' &amp;ne; ''y''</nowiki></code>
|-
| [[Approximate sign|Approx. equal]]
| {{pi}} &asymp; 3.14
| <code><nowiki>{{pi}} &amp;asymp; 3.14</nowiki></code><!-- should the pi be italic? -->
|-
| [[Less than sign|Less than]]
| ''x'' &lt; ''y''
| <code><nowiki>''x'' &amp;lt; ''y''</nowiki></code>
|-
| [[Less than or equal to|L.T. or equal]]
| ''x'' &le; ''y''
| <code><nowiki>''x'' &amp;le; ''y''</nowiki></code>
|-
| [[Greater than sign|Greater than]]
| ''x'' &gt; ''y''
| <code><nowiki>''x'' &amp;gt; ''y''</nowiki></code>
|-
| [[Greater than or equal to|G.T. or equal]]
| ''x'' &ge; ''y''
| <code><nowiki>''x'' &amp;ge; ''y''</nowiki></code>
|}
==Geographical coordinates==
<div style="float:right; width:100px;">{{Shortcut|WP:Coordinates|MOS:COORDS}}</div>
:'''For draft guidance on, and examples of, coordinates for linear features, see [[Wikipedia:WikiProject Geographical coordinates/Linear]]'''.
:'''Quick guide''':
{{coord how-to}}
 
[[Geographical coordinates]] on Earth should be entered using a template to standardise the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, a robot performs the functions automatically. 
First, [[Wikipedia:Obtaining geographic coordinates|obtain the coordinates]]. Avoid [[Wikipedia:WikiProject Geographical coordinates#Precision|excessive precision]].
Two types of template are available:
* {{tl|coord}} offers users a choice of display format through [[Help:User style|user style]]s, emits a [[Geo microformat]], and is recognised (in the ''title'' position) by the "nearby" feature of  Wikipedia's mobile apps and by external partners such as  Google (-Maps and -Earth) and Yahoo.
* Infoboxes such as {{tl|Infobox settlement}}, which automatically emit {{Tl|Coord}}.
The following formats are available. 
* For degrees only (including decimal values): {{tlc|coord|2={{var|dd}}|3={{var|N/S}}|4={{var|dd}}|5={{var|E/W}}}}
* For degrees/minutes: {{tlc|coord|2={{var|dd}}|3={{var|mm}}|4={{var|N/S}}|5={{var|dd}}|6={{var|mm}}|7={{var|E/W}}}}
* For degrees/minutes/seconds: {{tlc|coord|2={{var|dd}}|3={{var|mm}}|4={{var|ss}}|5={{var|N/S}}|6={{var|dd}}|7={{var|mm}}|8={{var|ss}}|9={{var|E/W}}}}
where:
* {{var|dd}}, {{var|mm}}, {{var|ss}} are the degrees, minutes and seconds, respectively;
* {{var|N/S}} is either ''N'' for northern or ''S'' for southern [[latitude]]s;
* {{var|E/W}} is either ''E'' for eastern or ''W'' for western [[longitude]]s;
* negative values may be used in lieu of ''S'' and ''W'' to denote southern and western [[hemisphere]]s
For example:
The city of [[Oslo]], located at '''59° 55&prime; N, 10° 44&prime; E''', enter:
:<code><nowiki>{{coord|59|55|N|10|44|E}}</nowiki></code>{{mdashb}}which becomes {{coord|59|55|N|10|44|E}}
For a country, like [[Botswana]], less precision is appropriate:
:<code><nowiki>{{coord|22|S|24|E}}</nowiki></code>{{mdashb}}which becomes {{coord|22|S|24|E}}
Higher levels of precision are obtained by using seconds:
:<code><nowiki>{{coord|33|56|24|N|118|24|00|W}}</nowiki></code>{{mdashb}}which becomes {{coord|33|56|24|N|118|24|00|W}}
Coordinates can be entered as decimal values
:<code><nowiki>{{coord|33.94|S|118.40|W}}</nowiki></code>{{mdashb}}which becomes {{coord|33.94|S|118.40|W}}
Increasing or decreasing the number of decimal places controls the precision. Trailing zeros should be used as needed to ensure that both values have the same level of precision. 
[[London Heathrow Airport]], [[ಆಂಸ್ಟರ್ಡ್ಯಾಮ್|Amsterdam]], [[Jan Mayen]] and [[Mount Baker]] are examples of articles that contain geographical coordinates.
Generally, the larger the object being mapped, the ''less precise'' the coordinates should be. For example, if just giving the location of a city, precision greater than 100{{nbsp}}meters is not needed unless specifying a particular point in the city, for example the central administrative building. Specific buildings or other objects of similar size would justify precisions down to 10{{nbsp}}meters or even one meter in some cases (1′′ ~15{{nbsp}}m to 30{{nbsp}}m, 0.0001° ~5.6{{nbsp}}m to 10{{nbsp}}m).
The final field, following the E/W, is available for attributes such as ''type'', ''region'' and ''scale''.
When adding coordinates, please remove the {{tl|coord missing}} tag from the article, if present. 
For more information, see [[Wikipedia:WikiProject Geographical coordinates|the geographical coordinates WikiProject]].
Templates other than {{tl|coord}} should use the following variable names for coordinates: {{var|lat_d}}, {{var|lat_m}}, {{var|lat_s}}, {{var|lat_NS}}, {{var|long_d}}, {{var|long_m}}, {{var|long_s}}, {{var|long_EW}}.
==See also==
* [[Wikipedia:Naming conventions (numbers and dates)]]
* [[Wikipedia:Date formattings]]
* [[m:Help:Date formatting feature]] at Meta
* {{section link|m:Help:Calculation|Displaying numbers and numeric expressions}} at Meta
{{Math templates}}
==Notes and references==
{{Reflist|35em}}
{{Style wide}}
[[ವರ್ಗ:General style guidelines]]
[[ವರ್ಗ:Wikipedia Manual of Style (formatting)]]
[[ವರ್ಗ:Wikipedia naming conventions|Dates and numbers]]