MOS:DATEUNIFY

This page guides the presentation of numbers, dates, times, measurements, currencies, coordinates, and similar material in articles. Its aim is to promote clarity and cohesion; this is especially important an article. The goal is to make the whole encyclopedia easier and more intuitive to use.
Where this manual provides options, consistency should be maintained within an article unless there is a good reason to do otherwise. The 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. If discussion cannot determine which style to use in an article, defer to the style used by the first major contributor.
==General notes==
===Quotations, titles, etc.===
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.
===Non-breaking spaces===
Guidance on the use of non-breaking spaces ("hard spaces")&nbsp;, , &thinsp;, is given in some sections below; may also be useful in controlling linebreaks in some situations. Not all situations in which hard spaces or may be appropriate are described. 
==Chronological items==
===Statements likely to become outdated===
Except on pages updated regularly (e.g. the "Current events" portal), terms such as , , , , , and should usually be avoided in favor of phrases such as , , and . For current and future events, use phrases like or to signal the time-dependence of the information.
Using will produce the text , with the additional benefit of putting the article in a category flagging it for periodic review. A full date is specified with . 
However, do not replace with because some information (the of 2005) would be lost; instead, make use of the template's alternate-text parameter: .
Relative-time expressions are acceptable for very long periods, such as geological epochs: 
=== Dates, months and years===
These requirements do not apply to dates in quotations or titles; . 
Special rules apply to citations; .
====Formats====
 Acceptable date formats
General use		Comments
 		
 		A comma follows the year unless followed by other punctuation that replaces the comma:
 		Omit year only where there is no risk of ambiguity:
 		Omit year only where there is no risk of ambiguity:
 		Use format only with Gregorian dates from 1583 onward.
 		
* Dates should be linked only when they are germane to the subject .
* For issues related to dates in sortable tables, , or consider using or 
* Phrases such as (or , but not ), , and are proper names, to which rules for dates do not apply (). 
 Unacceptable date formats (except in external titles and quotes)
Unacceptable	Acceptable	Comments
 	 	Do not add a dot to the day or to an abbreviated month
 	or 	Do not add a dot to the day or to an abbreviated month
 	or 	Months are capitalized
 	or 	Do not use ordinals (, , , etc.)
 	or 	Do not use a leading zero in month or day...
 	 	... except in all-numeric
 	 	Do not use separators other than hyphens
 	 	Do not abbreviate year to two digits
 	 	Do not use , or formats.
 	 	Do not use these formats.
 	 	Do not use theseformats.
 	 	No comma between month andyear
 	 	No comma between month andyear
 	 	Comma required between day andyear
 	 	Do not abbreviate year
 	 	Roman numerals are not normally used fordates
 	 	Years and days of the month are not normally written inwords
 	 	Years and days of the month are not normally written inwords
 	 	Do not zero-pad years
 	 	Use "in the year" only where needed for clarity
=====Consistency=====
* Dates in article body text should all use the same format: , but not .
* Publication dates in an article's citations should all use the same format, which may be:
** the format used in the article body text,
** an abbreviated format from the "Acceptable date formats" table, provided the day and month elements are in the same order as in dates in the article body, or
** the format expected in the citation style being used (however, all-numeric date formats other than must still be avoided).
: For example, publication dates within a single article might be in one, but only one, of these formats (among others):
:: 
:: 
* Access and archive dates in an article's citations should all use the same format, which may be:
** the format used for publication dates in the article;
** the format expected in the citation style adopted in the article (e.g. or 
** 
: For example, access/archive dates within a single article might be in one, but only one, of these formats (among others):
:: 
:: 
:: 
:When a citation style does not expect differing date formats, it is permissible to normalize publication dates to the article body text date format, and/or access/archive dates to either, with date consistency being preferred.
=====Strong national ties to a topic=====
* Articles on topics with strong ties to a particular English-speaking country should generally use the date format most commonly used in that nation. For the United States this is (for example) ; for most other English-speaking countries it is .
* Articles related to Canada or Israel may use either format with (as always) consistency within each article. 
* In some topic areas, the customary format differs from the usual national one: for example, articles on the modern U.S. military, including U.S. military biographical articles, use day-before-month, in accordance with U.S. military usage.
=====Retaining existing format=====
* If an article has evolved using predominantly one date format, this format should be used throughout the article, unless there are reasons for changing it based on strong national ties to the topic or consensus on the article's talk page.
* 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 the article's talk page.
* 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".
====Era style====
* The default calendar era is the Western Dionysian era system, a year numbering system also known as the Western Christian era (represented by ), or the Common Era (represented by ).
** and are the traditional ways of designating eras. and are common in some scholarly texts and in certain topic areas. Either convention may be appropriate for use in Wikipedia articles.
*** Use either the BCAD or the BCECE notation consistently within the same article. Exception: do not change direct quotations, titles, etc.
*** Do not change the established era style in an article unless there are reasons specific to its content. Seek consensus on the talk page 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.
*** and or and are written in upper case, unspaced, without a full stop (period, .), and separated from the numeric year by a space (, not ). It is advisable to use a non-breaking space.
*** may appear before or after a year (, ); the other abbreviations appear only after (, , ).
*** In general, do not use or unless required to avoid ambiguity (e.g. not nor ) or awkwardness not On the other hand, will avoid confusion, and depending on context one- and two-digit years may look more natural with an era marker (). Also, in the era marker makes it clear that 55 does not refer to the new king's age (or write ). If the era is shown for the initial date in a range, then use it for the final date as well: not but or (and definitely ). 
* Uncalibrated (bce) radiocarbon dates: Calibrated and uncalibrated dates can diverge widely, and some sources distinguish the two only via or (for calibrated dates) versus , or (uncalibrated). Avoid giving uncalibrated dates except in direct quotations, and even then a footnote or square-bracketed note [like this] should note that the date is uncalibrated or (ideally) give the calibrated date.
* BP or YBP: In scientific and academic contexts, BP (before present) or YBP (years before present) are often used. (Present in this context conventionally refers to January1, 1950.) Write or or but not forms such as and . If one of the abbreviated forms is used, link to Before present on first use: 
* 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: , or . 
** 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: 
====Julian and Gregorian calendars====
A date can be given in any appropriate calendar, as long as 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 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 Continent of Europe from 1582, the British Empire from 14September 1752, and Russia from 14February 1918 .
* Dates before 15October 1582 (when the Gregorian calendar was first adopted in some places) 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 should be assumed to be 1January .
* Dates for Roman history before 45BC 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 footnote).
At some places and times, the new year began on a date other than 1January. For example, in England and its colonies until 1752, the year began on Annunciation Day, 25March; . In writing about historical events, however, years should be assumed to have begun on 1January ; if there is reason to use another start-of-year date, this should be noted. 
If there is a need to mention 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).
====Ranges====
* Use a dash, or a word such as from or between, but not both: (not ); (not )
* A simple yearyear range is written using an en dash (&ndash; or ) not an em dash, hyphen or slash; this dash is (that is, with no space on either side); and the range's end year is usually given in full:
** ; (not ; )
** 
** Two-digit ending years (, but never or ) be used in any of the following cases: (1) two consecutive years; (2) infoboxes and tables where space is limited (using a single format consistently in any given table column); and (3) in certain topic areas if there is a very good reason, such as matching the established convention of reliable sources.
**The slash notation () may be used to signify a fiscal year or other special period, if that convention is used in reliable sources.
* Other "simple" ranges use an en dash as well:
** dayday: ; ; 
** monthmonth: ; ; (but uses a en dash; )
* If at least one of the items on either side of the en dash contains a space, then a en dash () is used:
** between specific dates in different months: ; 
** between dates in different years:
*** 
*** 
*** 
** between months in different years: ; 
***
** Where circa or other modifiers are used: 
* For ranges "to present", constructions such as (with unspaced ndash), (spaced ndash), or (spaced ndash) may be used, but other constructions may be more appropriate in prose . In tables and infoboxes where space is limited, pres. may be used (). Do not use incomplete-looking constructions such as and 
* For a person still living: , not or .Do not use * to indicate born; use b. only where space is limited e.g. tables and infoboxes; use either born or b. consistently in any given table column.
* Where birthdate is unknown: or Do not use † to indicate died; use d. only where space is limited, with consistency within any given table column.
* An overnight period may be expressed using a slash between two contiguous dates: or .Or use an en dash: (unspaced) ; (spaced) .
* The template can keep ages current in infoboxes and so on:
** {{age|1989|7|23}} returns: 
** {{age|1989|7|23}}-year-old returns: 
** {{age|1989|7|23}} years old returns: 
* Date mathematics templates are available for other age calculations.
====Uncertain, incomplete, or approximate dates====
* To indicate "around", "approximately", or "about", the use of the spaced, unitalicised form (or the template) is preferred over , , , , , or :
** 
** 
** 
* Where both endpoints of a range are approximate, c. should appear before each date (the two-argument form of does this):
** (not )
** (not )
* Where birth/death limits have been inferred from known dates of activity:
** 
** 
** 
* When a person is known to have been active ("flourishing") during certain years, , [[Floruit|fl.]], or may be used:
** 
: The linked forms should not be used on disambiguation pages, and "active" followed by the range is a better alternative for occupations not relating to the composition of works, whether it be musical, grammatical, historical, or any other such work.
* When a date is known to be either of two years (e.g. from a regnal or AH year conversion, or a known age at death):
** 
* Other forms of uncertainty should be expressed in words, either in article text or in a footnote: . Do not use a question mark (), because it fails to communicate the nature of the uncertainty.
* Ranges in which , , or similar forms appearwhether on one or both sidesemploy a spaced endash ({{snd}}) and ideally a non-breaking space should follow very short modifiers such as and . Examples: , , . Markup: , , 
===Times of day===
Context determines whether the 12- or 24-hour clock is used. In all cases, colons separate hours, minutes and (where present) seconds, e.g. or . Use figures () rather than words ().
* 12-hour clock times end with lower-case or , or or , preceded by a non-breaking space, e.g. or (markup: 2:30p.m. or 2:30pm), not or . Hours should not have a leading zero (e.g. , not ). Usually, use and rather than and ; whether "midnight" refers to the start or the end of a date should be explicitly specified unless clear from the context. Where several timesall a.m. or all p.m.appear in close proximity, then a.m. or p.m. need be given only once if there is no risk of confusion.
* 24-hour clock times have no a.m., p.m., noon or midnight suffix, and include a colon ( not ). Hours under 10 should have a leading zero (). The time refers to midnight at the start of a date, to noon, and to midnight at the end of a date, but should not be used for the first hour of the next day (e.g. use for ten minutes after midnight, not ).
Time zones
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 December7, 1941 (Hawaii time/date). Give priority to the place at which the event had its most significant effects; for example, if a hacker in the eastern hemisphere 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:
Alternatively, include just the UTC offset:
Rarely, the time zone in which a historical event took place has since changed; for example, China to 1949 was divided into 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 1960; 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.
===Days of the week===
* Days of the week are capitalized (, ).
===Seasons===
* Seasons are uncapitalized () except when personified: .
* Avoid the use of seasons to refer to a particular time of year () as such uses are ambiguous: the seasons are six months apart in the northern and southern hemispheres, and areas near the equator have only wet and dry seasons.
** Unambiguous alternatives include ; ; ; .
* Referring to a season by name is appropriate when it is part of a formal or conventional name or designation (; ; ; ; ; ).
===Decades===
* To refer to a decade as a chronological period (not with reference to a social era or cultural phenomenon), always use four digits as in . Do not use , , or (unless a possessive is actually meant).
** Prefixes should be hyphenated (; ).
* 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 , and do not write ; ; or ).
** A third alternative (where seen in reliable sources) is to spell the decade out, capitalized: .
===Centuries and millennia===
The sequence of numbered years in dates runs ; there is no "year zero".
* Treat the 1st century AD as years , the 17th century as , and the second millennium as ; similarly, the 1st century BC/BCE was BC/BCE, the 17th century BC/BCE was BC/BCE, and the second millennium BC/BCE.
* Centuries and millennia are identified using either "Arabic" numerals () or words (). When used adjectivally they contain a hyphen ( or ). 
* Do not capitalize (; ) 
* Do not use Roman numerals ().
* refers to the period (), while strictly refers either to () or ()
** When using forms such as , ensure that there is no ambiguity as to whether the century or just its first decade is meant.
* 
===Long periods of time===
* When the term is frequent, combine (years) or (years ago) with (thousand): , ; (million): , ; and (short-scale billion): , . 
* In academic contexts, SI annus-based units are often used: (kiloannus), (megaannus), and (gigaannus). 
* Show the meaning parenthetically, and consider linking to the appropriate section of the Year article on first occurrence and where the use is a standalone topic of interest. In source quotations, use square brackets: 
==Numbers==
===Numbers as figures or words===
Generally, in article text:
:
* Integers from zero to nine are spelled out in words.
* Integers greater than nine may be expressed either in numerals or in words ( or , or , or ). Numbers between 21 and 99 are hyphenated (including when part of a larger number): or but or .
* Other numbers are given in numerals (, ) or in forms such as . Markup: 
** Billion and trillion are understood to represent their short-scale values of 109(1,000,000,000) and 1012(1,000,000,000,000), respectively. Keep this in mind when translating articles from non-English Wikipedias, or using material from non-English or older sources.
** (unspaced, capitalized) or (unspaced) respectively may be used for "million" or "billion" after a number, when the word has been spelled out at the first occurrence ().
** SI prefixes and symbols, such as (), () and (), should be used only with units of measure as appropriate to the field, and not to express large quantities in other contexts. Examples of misuse: 
** Sometimes, the variety of English used in an article may suggest the use of a numbering system other than the Western thousands-based system. For example, the South Asian numbering system is conventionally used for certain things (especially monetary amounts) in South Asian English. This is discouraged in Wikipedia articles by .
*** When it is done anyway, for contextually important reasons, link the first spelled-out instance of each quantity (e.g. [[crore]], 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.
*** 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 . When converting a currency amount, use the exchange rate that applied at the time being written about; the template can be used for this purpose.
*** Group digits in Western thousands-based style (e.g., ; not ); .
*** 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. The choice and order of formats and conversions is a matter of editorial discretion and consensus at the article.
Notes and exceptions:
* Avoid beginning a sentence with a figure:
** Use: Or: 
** Not: 
** Use: 
** Not: (Nor: comparable numbers should be both written in words or both in figures.)
** Opening a sentence with a proper name or technical term that begins with a numeral can usually be avoided by rewording:
*** Prefer: Or: 
*** Avoid: 
* In tables and infoboxes, quantities are expressed in figures (); but numbers within a table's explanatory text and comments follow the general rule.
* Numbers in mathematical formulae are never spelled out (, not ).
* Sport scores and vote tallies should be given as figures, even if in the zero-to-nine range (; and ).
* Comparable quantities should be all spelled out or all in figures, even if one of the numbers would normally be written differently: , or , not 
* Adjacent quantities not comparable should usually be in or , not or .
** Avoid awkward juxtapositions: , not .
* Sometimes figures and words carry different meanings; for example, implies there is a single exception (without specifying which), while means that only locker number1 was not searched.
* Proper names, technical terms, and the like are never altered: , , , , , , , , , , , 
* Figures as figures: Use a figure when the figure itself (its glyph, shape, etc.) is meant: ; . 
* Only figures are used with unit ( not ), but figures or words may be used with unit ( or ), within the guidelines above. 
===Ordinals===
* Ordinal suffixes (, , , ) are not superscripted ( and , not nor ).
* For guidance on choosing between e.g. and , see .
* Regnal numbers are normally written with Roman numerals (without suffix, e.g. not ).
* Do not use a dot () or the ordinal mark () to indicate ordinals.
===Number ranges===
As with date ranges , number ranges in general, such as page ranges, should state the full value of both the beginning and end of the range, with an en dash between, e.g. or .
Forms such as and may be used where space is limited (such as in tables and infoboxes), or where a citation style formally requires it. (As usual, quotations are not changed.)
===Singular versus plural===
* Nouns following simple fractions are singular (; ; ).
* Nouns following mixed numbers are plural (; ).
* Nouns following the lone, unsigned digit 1 are singular, but those following other decimal numbers (i.e. base-10 numbers not involving fractions) are plural (; ; ; but ; ; ).
* The same rules apply to numbers given in words (; ; ; ).
===Fractions and ratios===
* Spelled-out fractions are hyphenated: .
* Where numerator and denominator can each be expressed in one word, a fraction is usually spelled out (e.g. ; ); use figures if a fraction appears with a symbol (e.g. markup: &nbsp;mi, not or ). A common exception is a series of values: .
* Mixed numbers are usually given in figures, unspaced (not or but markup: {{frac|8|1|2}}). In any case the integer and fractional parts should be consistent (not ).
* Metric (SI) measurements generally use decimals, not fractions (, not ).
* Non-metric (imperial and US customary) measurements may use fractions or decimals (;); the practice of reliable sources should be followed, and within-article consistency is desirable.
* In science and mathematics articles, mixed numbers are rarely used (use rather than ). The use of is discouraged in favor of one of these styles:
** \textstyle\frac{1}{2}markup: <math>\textstyle\frac{1}{2}</math>
** markup: 
** markup: 1/2
* Do not use special characters such as (deprecated markup: &frac12; or &#189;).
* Ordinal suffixes such as should not be used with fractions expressed in figures (not ; , but ; ; ).
*Dimensionless ratios (i.e. those without accompanying units) are given by placing a colon between integers, or placing to between numbers-as-words: or , not or 
**Use a colon (spaced) when one or more decimal points is present 
**Do not use the colon form where units are involved ()instead see ratios section of table at § Unit names and symbols, below.''
===Decimals===
* A period/full point (.), a comma, is used as the decimal point (, not ).
* Numbers between −1 and +1 require a leading zero (, not ); exceptions are sporting performance averages () and commonly used terms such as .
* Indicate repeating digits with an overbar e.g. gives . (Consider explaining this notation on first use.) Do not write e.g. because it resembles notation for uncertainty.
===Grouping of digits===
* Digits should be grouped and separated either by commas or by narrow gaps ( a period/full point).
*; Grouping with commas
*: Left of the decimal point, five or more digits are grouped into threes separated by commas (e.g.  ,  ,  ,  ).
*: Numbers with exactly four digits left of the decimal point may optionally be grouped (either    or  ), provided that this is consistent within each article.
*: When commas are used left of the decimal point, digits right of the decimal point are not grouped (i.e. should be given as an unbroken string).
*: Markup: produces this formatting.
*; Grouping with narrow gaps
*: Digits are grouped both sides of the decimal point (e.g.  ,  ,  ).
*: Digits are generally grouped into threes. Right of the decimal point, practice is to have a final group of four in preference to leaving an "orphaned" digit at the end (, but would also be acceptable). In mathematics-oriented articles long strings may be grouped into fives (e.g.  ).
*: This style is especially recommended for articles related to science, technology, engineering or mathematics.
*: Markup: Templates or may be used to produce this formatting. Note that use of space character as a separator in numbers, including non-breaking space, is problematic for screen readers. Screen readers read out each of digits as separate numbers (e.g.  30&thinsp;000  is read as "thirty zero zero zero".)
* Delimiting style should be consistent throughout a given article.
** Either use commas or narrow gaps, but not both in the same article.
** Either group the thousands in a four-digit number or do not, but not mixed use in the same article.
** However, grouping by threes and fives may coexist.
* An exception is made for four-digit page numbers or four-digit calendar years. These should never be grouped (not  ,  though    or  ).
===Percentages===
* In the body of non-scientific/non-technical articles, (American English) or (British English) are commonly used: ; ; . Ranges are written or , not or .
* In the body of scientific/technical articles, and in of any article, the symbol % (unspaced) is more common: , not or . Ranges: , not or .
* When expressing the difference between two percentages, do not confuse a percentage change with a change in percentage points.
===Scientific and engineering notation===
* Scientific notation always has a single nonzero digit to the left of the point: not , but . 
* Engineering notation is similar, but adjusted so that the exponent is a multiple of three: .
* Avoid mixing scientific and engineering notations (). 
* In a table column (or other presentation) in which all values can be expressed with a single power of 10, consider giving e.g. once in the column header, and omitting it in the individual entries. (Markup: {{e|7}})
* In both notations, the number of digits indicates the precision. For example, means rounded to the nearest thousand; to the nearest hundred; to the nearest ten; and to the nearest unit.
Markup: and may be used to format exponential notation.
===Uncertainty and rounding ===
* Where explicit uncertainty information (such as a margin of error) is available and appropriate for inclusion, it may be written in various ways:
** 
** (not used with scientific notation)
** 
** (equivalent to )
** 
** Markup: , , and may be used to format uncertainties.
* Where explicit (or is unimportant for the article's purposes) round to an appropriate number of significant digits; 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.
** 
** 
** (not )
** (not an official figure unlikely to be accurate at full precision)
** (unusual case in which the full-precision official figure is truly informative)
** (likely that accurate and precise figures were determined)
** (unlikely that any precise number can be accurate, even if an official figure is issued)
** (in reporting conflicting information, give detail sufficient to make the contrast intelligible)
** (not ). 
* The number of decimal places should be consistent within a list or context (, not ), unless different precisions are actually intended.
* It may sometimes be appropriate to note the of uncertainty information, especially where such information is normally provided and necessary for full interpretation of the figures supplied.
** 
* The 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.
** (heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle)
** ("about" because here the precise value is unknown, with substantial uncertainty)
* The reader may be assumed to interpret large round numbers () as approximations. Writing a quantity in words () can further emphasize its approximate nature.
* 
===Non-base-10 notations===
* In computer-related articles, use the prefix 0x for hexadecimal, 0 for octal, and 0b for binary, unless there is a strong reason to use some other notation. Explain these prefixes in the article's introduction or on first use.
* In all other articles, use <sub> to create subscripts: , . Markup: 9, 2013
* For bases above 10, use symbols conventional for that base (as seen in reliable sources) e.g. for base 16 use .
===Mathematical formulae===
For the display of a mathematical formula, there are multiple options, covered in detail at . One uses special MediaWiki markup using LaTeX syntax, which is capable of complex formulae; the other relies on conventionalized HTML formatting of simple formulae.
On the user end, the markup is displayed as a PNG image by default. Logged-in users can optionally have it rendered in MathML, or in HTML (via MathJax); detailed instructions are at Help:Displaying a formula.
Do not put markup in headings; it is an accessibility problem.
==Units of measurement==
===Unit choice and order===
Quantities are typically expressed using an appropriate "primary unit", displayed first, followed, when appropriate, by a conversion in parentheses e.g. . For details on when and how to provide a conversion, see the section . The choice of primary units depends on the circumstances, and should respect the principle of "strong national ties", where applicable:
* In non-scientific articles relating to the United States, the primary units are US customary, e.g. .
* In non-scientific articles relating to the United Kingdom, the primary units for most quantities are metric or other internationally used units, except that:
** UK engineering-related articles, including those on 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 – see next bullet);
** the primary units for distance/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 primary units for personal height and weight are feet/inches and stones/pounds;
** imperial pints are used for quantities of draught beer/cider and bottled milk;
* In all other articles, the primary units chosen will be SI units, 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 rotational speed, hands for heights of horses, et cetera).
* 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: .
** Or use about to emphasize which is the statutory, exact value: . 
* Nominal quantities (e.g. lumber) require consideration of whether the article is concerned with the item's actual dimensions or merely with its function. In some cases, 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.
* Whenever a conversion is used, ensure that the precision of the converted quantity in the article is comparable to the precision of the value given by the source .
* Where the article's primary units differ from the units given in the source, the template's |order=flip flag can be used; this causes the unit to be shown as secondary in the article, and the unit to be shown as primary: {{convert|200|mi|km|order=flip}} → 
===Unit conversions===
Where English-speaking countries use different units for the same quantity, provide a conversion in parentheses: ; . 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 US customary system, or vice versaand in particular, where those systems give a single term different definitionsa double conversion may be appropriate: (markup: {{convert|80|kg|lb stlb}}); (markup: {{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 ().
** When units are part of the subject of a topicnautical miles in articles about the history of nautical law (), SI units in scientific articles (), yards in articles about American footballit can be excessive to provide conversions every time a unit occurs. It might 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 similar to that of the source quantity value, so , not . Small numbers may need to be converted to a range where rounding would cause a significant distortion, so , not . 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). 
* Conversion templates can be used to convert and format many common units, including , 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. 
* may be added to articles needing general attention regarding choice of units and unit conversions.
* Avoid edit-warring over unit conversions, or performing mass conversions from one unit style to another across many articles; sanctions may apply.
===Unit names and symbols===
:
:* Examples of unit names: foot, metre, kilometre, (meter, kilometer US).
:* 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. ).
** Exception: Certain units are generally represented by their symbols (e.g. rather than ) even on first use, though their unit names may be used for emphasis or clarity ().
** Exception: Consider using inches (but not in.) in place of in where the latter might be misread as a prepositionbut not where the value is followed by a parenthesized conversion e.g. , or is part of such a conversion ().
* Where space is limited, such as in tables, infoboxes, parenthetical notes, and mathematical formulas, unit symbols are preferred.
* Units unfamiliar to general readers should be presented as a namesymbol pair on first use, linking the unit name ().
* Ranges use unspaced en dash () if only one unit symbol is used at the end (e.g. ), and spaced en dash () if two symbols are used (e.g. ); 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. , , and are all acceptable).
* Lengthwidth, lengthwidthheight and similar dimensions may be separated by the multiplication sign (× or &times;) or the word .
** With the multiplication sign, each number should be followed by a unit name or symbol (if appropriate):
*** , not , , nor 
*** 
***
** The symbol is preceded by a space (preferably non-breaking), and followed by a space (which may also be non-breaking in short constructions).
** With , the unit need be given only once if it is the same for all values: or 
** The unspaced letter may be used in common terms such as .
* Do not use unit symbol characters, such as those found in the CJK Compatibility block of Unicode (e.g.: ㎓, ㎦). Support for them in Western fonts is not widespread.
 
Aspect 	Guideline 	Acceptable 	Unacceptable
Unit names and symbols	Except as listed in the table below, unit are uncapitalized unless they are derived from a proper name, in which case the first letter (of the base unit symbol, not of any prefix) is capitalized. 	 	
Unit names and symbols	Unit symbols are undotted. 	 	
Unit names and symbols	Unit are given in lower case except: where any word would be capitalized, or where otherwise specified in the SI brochure Tables 6, 7, 8, and 9 give additional guidance on non-SI units. or this Manual of Style.	 	
Unit names and symbols	The spelling of certain unit names (some of which are listed in , below) varies with the variety of English followed by the article. 	 	
Unit names and symbols	Write unit names and symbols in upright () type, except where emphasizing in context. 	 	
Unit names and symbols	Write unit names and symbols in upright () type, except where emphasizing in context. 	 	
Numeric values 	Do not spell out numbers before unit ... 	 	
Numeric values 	...but words figures may be used with unit . 	 	
Numeric values 	Values with no accompanying unit are usually given in figures. 	 	
Numeric values 	Use a non-breaking space ( or &nbsp;) between a number and a unit , or use ... 	(markup: 29&nbsp;kg or ) 	
Numeric values 	... though with certain symbols no space is used (see "Specificunits" table below)... 	 	
Numeric values 	... and a normal space is used between a number and a unit . 	(markup: 29 kilograms) 	
Numeric values 	To form a value and a unit into a compound adjective use a hyphen or hyphens... 	 	
Numeric values 	... but a non-breaking space (never hyphen) separates a value and unit . 	 	
Plurals 	SI unit are pluralized by adding the appropriate or suffix... 	; 	
Plurals 	... except for these irregular forms. 	; ; ; ; 	
Plurals 	Some non-SI units have irregular plurals. 	; 	
Plurals 	Some non-SI units have irregular plurals. 	; (unusual) 	
Plurals 	Unit (in any system) are identical in singular and plural. 	 	
Powers 	Format exponents using , not special characters. 	(markup: km<sup>2</sup>)	(km&#178;)
Powers 	Or use or ( the unit being modified). 	 	
Powers 	For areas or volumes only, or may be used ( the unit being modified). 	 	
Powers 	For areas or volumes only, or may be used ( the unit being modified). 	 	
Powers 	or may be used with US customary or imperial units, but not with SI units. 	 	
Products 	Indicate a product of unit with either a hyphen or a space. 	 	
Products 	Indicate a product of unit with &sdot; or &nbsp;. 	 	
Products 	In some topic areas, such as power engineering, certain products take neither space nor &sdot;. Follow the practice of reliable sources in the article's topic area. 	 	
Products 	To pluralize a product of unit , pluralize only the final unit. (Unit are never pluralized.) 	 	
Ratios,Rates,Densities	Indicate a ratio of unit with . 	 	
Ratios,Rates,Densities	Indicate a ratio of unit with a forward slash (/), followed by either a single symbol or a parenthesized product of symbolsdo not use multiple slashes. Or use−1,−2, etc. 	 	
Ratios,Rates,Densities	Indicate a ratio of unit with a forward slash (/), followed by either a single symbol or a parenthesized product of symbolsdo not use multiple slashes. Or use−1,−2, etc. 	 	
Ratios,Rates,Densities	To pluralize a ratio of unit , pluralize only the numerator unit. (Unit are never pluralized.) 	 	
Ratios,Rates,Densities	Some of the special forms used in the imperial and US customary systems are shown here... 	 	
Ratios,Rates,Densities	... but only the slash or negative exponent notations are used with SI (and other metric) units. 	 	
Ratios,Rates,Densities	... but only the slash or negative exponent notations are used with SI (and other metric) units. 	 	
Prefixes 	Prefixes should not be separated by a space or hyphen. 	 	
Prefixes 	Prefixes are added without contraction, except as shown here: 	 	
Prefixes 	The , , , and prefixes should generally be avoided; exceptions include centimetre, decibel, hectolitre, hectare, and hectopascal. 	 	
Prefixes 	Do not use for 103, for 106, or for 109 (except as noted elsewhere on this page for and , e.g. for monetary values) 	 	
Mixedunits 	Mixed units are traditionally used with the imperial and US customary systems... 	 	
Mixedunits 	Mixed units are traditionally used with the imperial and US customary systems... 	 	
Mixedunits 	... and in expressing time durations... 	 	
Mixedunits 	... but are not normally used in SI. 	 	
===Specific units===
* The following table lists only units that need special attention.
* The SI Brochure should be consulted for guidance on use of other SI and non-SI units.
 Guidelines on specific units
Group 	Name 	Symbol 	Comment
Length,Speed 	 	 	Do not use &prime;(), &Prime;(), apostrophe() or quote().
Length,Speed 	foot per second 	( ) 	
Length,Speed 	hand 	or 	Equal to 4 inches; used in measurement of horses. A dot may be followed by additional inches e.g. indicates
Length,Speed 	knot 	( or )	
Length,Speed 	 	 	
Length,Speed 	micron 	( ) 	Markup: &mu;m Link to micrometre (for which micron is a synonym) on first use.
Length,Speed 	astronomical unit	 	The preferred option is . Articles that already use may switch to au or continue with AU; seek consensus on the talk page.
Length,Speed 	 	 	In nautical and aeronautical contexts use rather than mile to avoid confusion with nautical mile.
Volume,Flow 	 	 	Markup: cm3
Volume,Flow 	 	 	Non-SI symbol used for certain engine displacements; link to Cubic centimetre on first use.
Volume,Flow 	 	 	or (or ) must be specified; or must be specified for fluid ounces and US units, except with gallon. (Without , ounce is ambiguousversus avoirdupois ounce or troy ounceand US pint or US quart are ambiguousversus US dry pint or US dry quart.)
Volume,Flow 	cubic foot 	( ) 	Write , , or , not .
Volume,Flow 	 	( ) 	
Volume,Flow 	 	or 	The symbol l (lowercase "el") in isolation (i.e. outside forms as ml) is easily mistaken for the digit1 or the capital letterI("eye").
Mass,Force,Density,Pressure	 	 	Spell out in full.
Mass,Force,Density,Pressure	 	 	
Mass,Force,Density,Pressure	 	 	
Mass,Force,Density,Pressure	troy ounce 	 	or must be specified. Articles about precious metals, black powder, and gemstones should always specify whether ounces and pounds are avoirdupois or troy.
Mass,Force,Density,Pressure	troy pound 	 	or must be specified. Articles about precious metals, black powder, and gemstones should always specify whether ounces and pounds are avoirdupois or troy.
Mass,Force,Density,Pressure	carat 	 	Used to express masses of gemstones and pearls.
Purity 	carat or karat 	or 	A measure of purity for gold alloys. (Do not confuse with the unit of mass with the same spelling.)
Time 	 	 	Do not use &prime;(), &Prime;(), apostrophe() or quote() for minutes or seconds. See also the hours–minutes–seconds formats for time durations described in the Unit names and symbols table.
Time 	year 	 	Use only with an SI prefix multiplier (, not ).
Time 	year 	or 	
Infor­mation, Data 	bit 	 	Do not confuse bit/second or byte/second with baud (Bd).
Infor­mation, Data 	byte 	 	Do not confuse bit/second or byte/second with baud (Bd).
Infor­mation, Data 	bit per second 	( , ) 	Do not confuse bit/second or byte/second with baud (Bd).
Infor­mation, Data 	byte per second 	or 	Do not confuse bit/second or byte/second with baud (Bd).
Angle 	 	 	
Angle 	arcminute 	 	Markup: &prime; (prime ′ not apostrophe/single quote).
Angle 	arcsecond 	 	Markup: &Prime; (double prime ″ not double-quote).
Angle 	degree 	 	Markup: &deg; (degree ° not masculine ordinal or ring ).
Temp­erature 	degree 	 	Markup: &deg;. Use a non-breaking space: , not nor
Temp­erature 	degree Celsius 	( ) 	Markup: &deg;. Use a non-breaking space: , not nor
Temp­erature 	kelvin 	( ) 	
Energy 	 	 	In certain subject areas, calorie is conventionally used alone. Articles following this practice should specify on first use whether the use refers to the small calorie or to the kilocalorie (large calorie). Providing conversions to SI units (usually calories to joules or kilocalories to kilojoules) may also be useful. A kilocalorie () is 1000 calories. A calorie (small calorie) is the amount of energy required to heat 1 gram of water by 1 °C. A kilocalorie is therefore also a kilogram calorie.
Energy 	 	 	In certain subject areas, calorie is conventionally used alone. Articles following this practice should specify on first use whether the use refers to the small calorie or to the kilocalorie (large calorie). Providing conversions to SI units (usually calories to joules or kilocalories to kilojoules) may also be useful. A kilocalorie () is 1000 calories. A calorie (small calorie) is the amount of energy required to heat 1 gram of water by 1 °C. A kilocalorie is therefore also a kilogram calorie.
====Quantities of bytes and bits ====
In quantities of bits and bytes, the prefixes (symbol or ), (), (), (), etc., are ambiguous. They may be based on a decimal system (like the standard SI prefixes), meaning 103, 106, 109, 1012, etc., or they may be based on a binary system, meaning 210, 220, 230, 240, etc. The binary meanings are more commonly used in relation to solid-state memory (such as RAM), while the decimal meanings are more common for data transmission rates, disk storage and in theoretical calculations in modern academic textbooks.
Follow these recommendations when using these prefixes in Wikipedia articles:
* Following the SI standard, a lower-case should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital 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 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 ( 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 rates, 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:
** 
** 
** 
* Avoid inconsistent combinations such as . Footnotes, such as those seen in , may be used for disambiguation.
* Unless explicitly stated otherwise, one byte is eight bits .
The IEC prefixes (symbol ), (), (), etc., are generally not to be used except:
* 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; or
* 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.
==Currencies and monetary values==
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 ( on first use, generally thereafter), euros (), or pounds sterling ().
Currency names
* Do not capitalize the names or denominations of currencies, currency subdivisions, coins and banknotes: not but . Exception: where otherwise required, as at the start of a sentence or in such forms as .
* To pluralize use the standard English plurals (), not the invariant plurals used for European Union legislation and banknotes (). For the adjectival form, use a hyphenated singular (). 
* Link the first occurrence of lesser-known currencies ().
Currency symbols
* In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. ), with subsequent references using just the appropriate symbol (e.g. ), unless this would be unclear. 
** 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) use the full signifier (e.g. , ) 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 (, or ), unless this would be unclear.
* The pound sterling is represented by the symbol, with one horizontal bar. The double-barred 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£) use the symbol conventionally preferred for that currency.
* If there is no common English abbreviation or symbol, follow the ISO 4217 standard. 
Formatting
* A period (full stop, .) is used as the decimal pointnever a comma (, not ).
* 
* Do not place a currency symbol the accompanying numeric figures (e.g. , , ) unless that is the normal convention for that symbol when writing in English: . Never use forms such as or .
* Currency abbreviations that come before the numeric value are if they consist of a nonalphabetic symbol only, or end in a symbol (; ); but if alphabetic ().
* Ranges should be expressed giving the currency signifier just once: , not .
* and should be spelled out on first use, and (optionally) abbreviated or (both unspaced) thereafter: ; .
* In general, a currency symbol should be accompanied by a numeric amount e.g. not but or .
** Exceptions may occur in tables and infoboxes where space is limited e.g. . It may be appropriate to wikilink such uses, or add an explanatory note.
Conversions
* Conversions of may be provided in terms of more familiar currenciessuch as the US dollar, euro or pound sterlingusing an appropriate rate (which is often 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. , not 
* For , 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. 
==Common mathematical symbols==
* The Insert menu below the editing window gives a more complete list of math symbols, and allows symbols to be inserted without the HTML encoding (e.g. &divide;) shown here.
* Spaces are placed to left and right when a symbol is used (), but no space is used when ().
* Use or for variable names: {{var|base}} + {{var|ht}} and base + ht both produce + .
* The and templates may be used to prevent awkward linebreaks.
Common mathematical symbols
Symbol name 	Example 	Markup 	Comments
Plus /positive 	+ 	{{var|x}} + {{var|y}} 	
Plus /positive 	+ 	+{{var|y}} 	
Minus /negative 	− 	{{var|x}} − {{var|y}} 	Do not use hyphens () or dashes (
Minus /negative 	− 	−{{var|y}} 	Do not use hyphens () or dashes (
Plus-minus /minus-plus	41.5 ± 0.3	41.5 ± 0.3 	
Plus-minus /minus-plus	 	 	
Multiplication,cross 	× 	{{var|x}} × {{var|y}} 	Do not use the letter to indicate multiplication. However, an may be used as a substitute for "by" in common terms such as .
Division, obelus 	÷ 	{{var|x}} ÷ {{var|y}}	
Equal / equals 	= 	{{var|x}} = {{var|y}} 	
Not equal 	≠ 	{{var|x}} ≠ {{var|y}} 	
Approx. equal 	≈ 3.14 	{{pi}} ≈ 3.14 	
Less than 	< 	{{var|x}} < {{var|y}} 	
Less or equal 	≤ 	{{var|x}} ≤ {{var|y}} 	
Greater than 	> 	{{var|x}} > {{var|y}} 	
Greater or equal 	≥ 	{{var|x}} ≥ {{var|y}} 	
==Geographical coordinates==
:
:Quick guide:
 
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, obtain the coordinates. Avoid excessive precision.
The template offers users a choice of display format through user styles, emits a Geo microformat, and is recognised (in the position) by the "nearby" feature of Wikipedia's mobile apps and by external service providers such as Google Maps and Google Earth, and Yahoo. Infoboxes automatically emit .
The following formats are available. 
* For degrees only (including decimal values): 
* For degrees/minutes: 
* For degrees/minutes/seconds: 
where:
* , , are the degrees, minutes and seconds, respectively;
* is either N for northern or S for southern latitudes;
* is either E for eastern or W for western longitudes;
* negative values may be used in lieu of S and W to denote Southern and Western Hemispheres
For example:
For the city of Oslo, located at 59° 55′ N, 10° 44′ E:
: {{coord|59|55|N|10|44|E}}which becomes 
For a country, like Botswana, less precision is appropriate:
: {{coord|22|S|24|E}}which becomes 
Higher levels of precision are obtained by using seconds:
: {{coord|33|56|24|N|118|24|00|W}}which becomes 
Coordinates can be entered as decimal values
: {{coord|33.94|S|118.40|W}}which becomes 
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, Amsterdam, Jan Mayen and Mount Baker are examples of articles that contain geographical coordinates.
Generally, the larger the object being mapped, the the coordinates should be. For example, if just giving the location of a city, precision greater than 100meters 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 10meters or even one meter in some cases (1′′ ~15m to 30m, 0.0001° ~5.6m to 10m).
The final field, following the E/W, is available for attributes such as type:, region:, or scale: .
When adding coordinates, please remove the tag from the article, if present. 
Templates other than should use the following variable names for coordinates: , , , , , , , .
==See also==
* Wikipedia:Naming conventions (numbers and dates)
* Wikipedia:Date formattings
* m:Help:Date formatting feature at Meta
* at Meta
==Notes==
==References==
Category:Wikipedia Manual of Style (formatting)
Dates and numbers