Wikipedia:Manual of Style/Dates and numbers

This part of the 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 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.

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.

Non-breaking spaces

Guidance on the use of non-breaking spaces (also called "hard spaces"; markup: {{nbsp}} or  ) is given in some of the sections below, though not all situations in which nbsp may be appropriate are described. {{nobreak}} may also be useful in some situations. For further information see Wikipedia:Manual of Style § Non-breaking spaces and Wikipedia:Line-break handling.

Chronological items

Statements likely to become outdated

See also: Wikipedia:As of and Wikipedia:Manual of Style/Words to watch § Relative time references

Except on pages updated regularly (e.g. current events), terms such as now, soon, currently, and recently should usually be avoided in favor of phrases such as during the 1990s and in August 1969. For future and current events, use phrases such as as of November 2024 or since the beginning of 2010 to signal the time-dependence of the information. Or (for example) {{as of|2024}} will produce the text As of 2024 and adds the article to a category flagging it for periodic review. However, do not replace (for example) since the start of 2005 with {{as of|2005}} because some information (the start of 2005) would be lost; advanced features of {{as of}} such as {{as of|2005|alt=since the start of 2005}} can be used in such circumstances.

Relative-time expressions are acceptable for very long periods, such as geological epochs: Humans diverged from apes long ago, but only recently developed state legislatures.

Time of day

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (e.g. 1:38:09 pm or 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. 2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Hours denoted by a single digit should not have a leading zero (e.g. 2:30 p.m., not 02:30 p.m.). A hard space (see above) is advisable (2:30 pm or {{nowrap|2:30 p.m.}}). Use noon and midnight rather than 12 pm and 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. 08:15). 00:00 refers to midnight at the start of a date, 12:00 to noon, and 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 00:10 for ten minutes after midnight, not 24:10).

The numerical elements of times-of-day are figures (12:45 p.m.) rather than words (twelve forty-five p.m.) though conventional terms such as noon and midnight are acceptable (taking care, with the latter, to avoid possible date ambiguity in constructions such as midnight on July 17).

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 December 7, 1941 (Hawaii time/​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:

  •   8 p.m. Eastern Standard Time on January 15, 2001 (01:00 UTC, January 16)

Alternatively, include just the UTC offset:

  •  21:00 British Summer Time (UTC+1) on 27 July 2012

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 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.

Dates and years

These requirements do not apply to dates in quotations or titles. Special rules apply to citations; see Wikipedia:Citing sources § Citation style.

Formats

Date formats

Acceptable date formats

General use	Only where brevity is required (references, tables, lists, etc.)	Comments
22 August 2001	22 Aug 2001
August 22, 2001	Aug 22, 2001	A comma follows the year unless followed by other punctuation: The weather on September 11, 2001, was clear and warm Everyone remembers July 21, 1969‍—‌when man landed on the Moon
22 August	22 Aug	Omit year only where there is no risk of ambiguity: In 2013, Ramadan began on 10 July and ended on 7 August January 1 is New Year's Day
August 22	Aug 22
No equivalent for general use	2001-08-22	Use only with Gregorian dates between 1583 and 9999

• The routine linking of dates is deprecated. Dates should be linked only when they are germane to the subject, as discussed at Wikipedia:Linking § Chronological items.
• For issues related to dates in sortable tables, see Date sorting problems or consider using {{sort|2008-11-01|1 Nov 2008}} or {{dts|Nov 1, 2008}}.
• Phrases such as Fourth of July (or July Fourth, but not July 4th), Cinco de Mayo, Seventh of March Speech and Sete de Setembro are proper names, to which rules for dates do not apply (Every Fourth of July celebration includes fireworks).

Unacceptable date formats (except in external titles and quotes)

Acceptable	Unacceptable	Comments
9 June or June 9	June 9th 9th June the 9th of June	Do not use 1st, 2nd, 3rd, etc.
	9. June	Do not add a dot to the day
	09 June June 09	Do not "zero-pad" month or day, except in all-numeric (yyyy-mm-dd) format
2007-04-15	2007-4-15
	2007/04/15	Do not use separators other than hyphen
	15-04-2007 04-15-2007	Do not use dd-mm-yyyy or mm-dd-yyyy formats, as they are ambiguous for some dates
July 2001	7-2001 07-2001 2001 July July of 2001	Do not use these formats
	2001-07 2001–07	May be misinterpreted as the range of years 2001 to 2007; 2001–07 is acceptable if referring to the range of years
	July, 2001	No comma between month and year
3 July 2001	3 July, 2001
July 3, 2001	July 3 2001	Comma required between day and year
the 2002 elections	the '02 elections	Do not use an apostrophe to abbreviate year
Copyright 2002	Copyright MMII	Roman numerals are not normally used for dates
2001	Two thousand one	Years and days of the month are not normally written in words
May 1 or 1 May	the first of May May the first
sold in 1995	sold in the year 1995	Use "in the year" only where needed for clarity (About 1800 ships arrived in the year 1801)

Note to table:

Consistency

• Dates in article body text should all use the same format: She fell ill on 25 June 2005 and died on 28 June, but not She fell ill on 25 June 2005 and died on June 28.
• Publication dates in an article's citations should all use the same format, which may be

• any format from the "Acceptable date formats" table, or
• formats required by the citation style being used.
• However, all-numeric date formats other than yyyy-mm-dd must still be avoided.

For example, a single article might contain either:

Jones, J. (20 Sep 2008), or

Smith, J. (Sep 2002)

but not both:

Jones, J. (20 Sep 2008), and

Smith, J. (September 2002)

• Access and archive dates in an article's citations should all use the same format, which may be:

• 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:

Jones, J. (20 Sep 2008) ... Retrieved 5 Feb 2009., or

Jones, J. (20 Sep 2008) ... Retrieved 2009-02-05.

but not more than one of:

Jones, J. (20 Sep 2008) ... Retrieved 5 February 2009.,

Jones, J. (20 Sep 2008) ... Retrieved Feb 5, 2009., and

Jones, J. (20 Sep 2008) ... Retrieved February 5, 2009.

Strong national ties to a topic

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.

Retaining existing format

See also: 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".

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 BC and AD), or the Common Era (represented by 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 (5 BC, not 5BC). It is advisable to use a non-breaking space.
    • AD may appear before or after a year (AD 106, 106 AD); the other abbreviations appear after (106 CE, 3700 BCE, 3700 BC).
    • Do not use CE or AD unless required to avoid ambiguity (e.g. "The Norman Conquest took place in 1066" not 1066 CE nor AD 1066). On the other hand, "Plotinus was a philosopher living at the end of the 3rd century AD" will avoid unnecessary confusion. Also, in "He did not become king until 55 CE" the era marker makes it clear that "55" does not refer to his age. Alternatively, "He did not become king until the year 55."
    • Use either the BC–AD or the BCE–CE notation consistently within the same article. Exception: do not change 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 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, 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 BP). BP years are given as 18,000 BP or spelled out as 18,000 years before present (not 18,000 YBP, 18,000 before present, 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 AH (836 CE)" or "in 836 AD (221 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: "The March equinox passed into Pisces in year −67."

Julian and Gregorian calendars

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 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 14 September 1752, and Russia from 14 February 1918 (see Gregorian calendar).
• Dates before 15 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 should be assumed to be 1 January (see below for more details).
• Dates for Roman history before 45 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 footnote).

At some places and times, the new year began on a date other than 1 January. For example, in England and its colonies until 1752, the year began on Annunciation Day, 25 March; see the New Year article for other styles. In writing about historical events, however, years should be assumed to have begun on 1 January (see the example of the execution of Charles I in "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 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

• A pure year–year range is written (as is any range) using an en dash (– or {{ndash}}), 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:

  •   1881–86;  1881–92 (not 1881–6;  1881 – 86)

Markup: 1881{{ndash}}86 or 1881–86

But both years are given in full in the following cases:

• birth–death parentheticals: Petrarch (1304–1374) was ...;  not (1304–74)
• different centuries: 1881–1903;  not 1881–03
• starting year before 1000 AD: 355–372 (not 355–72);  95–113;  95–113 AD;  982–1066;  2590–2550 BCE;  1011–922 BC

Markup: 1011{{ndash}}922{{nbsp}}BC

• spanning from BC/BCE to AD/CE: 42 BC – 15 AD (note spaced en dash)

Markup: 42{{nbsp}}BC{{snd}}15{{nbsp}}AD or 42 BC – 15 AD

Other notes:

• Periods straddling two different years, including sports seasons, are generally written with the range notation (2005–06). The slash notation (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 2005–2010.

• Other "pure" ranges use an unspaced en dash as well:

• day–day: 5–7 January 1979;  January 5–7, 1979;  elections were held March 5–8
• month–month: the 1940 peak period was May–July;  the peak period was May–July 1940;  (but the peak period was May 1940 – July 1940 uses a spaced en dash‍—‌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 ({{snd}}) is used:

• between specific dates in different months: They travelled June 3 – August 18, 1952;  They travelled 3 June – 18 August 1952
• between dates in different years:

Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist ...

Markup: 12{{nbsp}}February 1809{{snd}}19{{nbsp}}April 1882 or 12 February 1809 – 19 April 1882

Abraham Lincoln (February 12, 1809 – April 15, 1865) was the 16th President of ...

• between months in different years: The exception was in force August 1892 – January 1903;  The Ghent Incursion (March 1822 – January 1, 1823) was ended by the New Year's Treaty

Markup: March 1822{{snd}}January{{nbsp}}1, 1823 or March 1822 – January 1, 1823

• For a person still living: Serena Williams (born September 26, 1981) is a ..., not (September 26, 1981–) or (born on September 26, 1981)
• An overnight period may be expressed using a slash between two contiguous dates: the night raids of 30/31 May 1942 or raids of 31 May / 1 June 1942.

Or use an en dash: raids of 30–31 May 1942;  raids of 31 May – 1 June 1942.

• Use a dash, or a word such as from or between, but not both: from 1881 to 1886 (not from 1881–86);  between June 1 and July 3 (not between June 1 – July 3)

Use 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, use of the spaced, unitalicised form c. 1291 (or the {{circa}} template) is preferred over circa, ca, ca., approximately, or approx.:

  •   At the birth of Roger Bacon (c. 1214) ...

  •   John Sayer (c. 1750 – 2 October 1818) ...

  •   the Igehalkid dynasty of Elam, c. 1400 BC ...

• Where both endpoints of a range are approximate, c. should appear before each date:

  •   Dionysius Exiguus (c. 470 – c. 540) ... (not Dionysius Exiguus (c. 470 – 540) ...)

  •   Rameses III (reigned c. 1180 – c. 1150 BCE) ... (not Rameses III (reigned c. 1180 – 1150 BCE) ...)

• Where birth/death dates have been extrapolated from known dates of activity:

  •   Offa of Mercia (before 734 – 26 July 796) ...

  •   Robert Menli Lyon (1789 – after 1863) ...

  •   Ambrose Gwinnett Bierce (June 24, 1842 – after December 26, 1913) ...

• When a person is known to have been active ("flourishing") during certain years, fl., [[floruit|fl.]], or {{fl.}} may be used:

  •   Osmund (fl. 760–772) ...

  •   Aethelwalh (fl. c. 660 – 685) ...

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.

• 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):

  •   Anne Smith (born 1912 or 1913; died 2013) ...

• Other forms of uncertainty should be expressed in words, either in article text or in a footnote: April 14, 1224 (unattested date). Do not use a question mark (1291?) for such purposes, as this fails to communicate the nature of the uncertainty.

Other periods

Days of the week

• Days of the week are capitalized (Sunday, Wednesday).

Months

• Months are normally expressed as capitalized whole words (e.g. March).

• Write March 2001, not March of 2001 or March, 2001.
• Three-letter abbreviations such as 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.

• Do not express months as numbers (monthly sales peaked in 3/2001).

• An exception is the YYYY-MM-DD format e.g. 2001-03-05 for March 5, 2001 (but note that this format has restricted use‍—‌see § Date formats).
• Do not use YYYY-MM format, because it can be mistaken for a range of years (2001-03, if used to denote March 2001, may be misread as referring to the years 2001–2003).

Seasons

• Seasons are uncapitalized (a hot summer) except when personified: Soon Spring will show her colors; Old Man Winter.
• Because the seasons are reversed in the northern hemisphere versus the southern (and areas near the equator may have wet and dry seasons instead) it is preferable to avoid such references as winter 1995 in favor of (for example) early 1995;  the first quarter of 1995;  January to March 1995, even where a particular location is involved.

• Reference to seasons may be appropriate when related to the point being made (the autumn harvest;  migration typically begins in mid-spring).

Decades

• 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 (the 1980s, but not the 1980's or the 1980‑ies, and definitely not the 1980s').

• Prefixes should be hyphenated (the mid‑1980s;  pre‑1960s social attitudes).

• 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 (the Roaring '20s,  the Gay '90s,  condemning the '60s counterculture, but grew up in 1960s Boston, moving to Dallas in 1971, and do not write the 90's;  the 90s;  or the 90s').
• A third alternative (where seen in reliable sources) is to spell the decade out, capitalized: changing attitudes of the Sixties

Centuries and millennia

• Treat the 1st century AD as years 1–100, the 17th century as 1601–1700, and the second millennium as 1001–2000; similarly, the 1st century BC/BCE was 100–1 BC/BCE, the 17th century was 1700–1601 BC/BCE, and the second millennium 2000–1001 BC/BCE.
  • The 18th century (1701–1800) and the 1700s (1700–1799) are not the same period.
  • When using forms such as the 1700s ensure there is no ambiguity as to whether e.g. 1700–1709, or 1700–1799, is meant.
  • Note that the sequence of years runs ... 2 BC, 1 BC, 1 AD, 2 AD ...‍—‌there is no "year 0".
• Centuries and millennia are identified using either figures (the 18th century, not XVIII century) or words (the second millennium). When used adjectivally they contain a hyphen (nineteenth-century painting or 19th-century painting). Do not capitalize (the best Nineteenth-century paintings;  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, 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, or might be a standalone topic of interest. For source quotations use square brackets, as in "a measured Libby radiocarbon date of 35.1 mya [million years ago] required calibration ..."

Numbers

Numbers as figures or words

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 (16 or sixteen, 84 or eighty-four, 200 or two hundred). In spelling out numbers, "components" from 21 to 99 are hyphenated; larger ones are not (fifty-six, five hundred).
• Other numbers are given in numerals (3.75, 544) or in forms such as 21 million. Markup: 21{{nbsp}}million

• 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.
• M (unspaced) and bn (unspaced) may be used for million and billion after spelling out the first occurrence (e.g. She received £70 million and her son £10M).
• SI prefixes and symbols, such as giga- (G) and tera- (T), should be restricted to use in scientific and engineering expressions.
• Sometimes, the 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 convention­ally used in South Asian English. In those situations, 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.) 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 three crore (thirty million). Group digits in Western thousands-based style (e.g., 30,000,000; not 3,00,00,000): see § 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.)

Notes and exceptions:

• In tables and infoboxes quantities are expressed in figures (Years in office: 5); but numbers within a table's explanatory text and comments follow the general rule.
• Numbers in mathematical formulae are never spelled out (3 < π < 22/7, not three < π < 22 sevenths).
• Comparable quantities should be all spelled out or all in figures:

  •  five cats and thirty-two dogs, not five cats and 32 dogs.

  •  86 men and 103 women, not eighty-six men and 103 women

  •  There were 3 deaths and 206 injuries (even though 3 would normally be given as three) or Three died and two hundred six were injured (even though two hundred six would normally be given as 206), not There were three deaths and 206 injuries

• But adjacent quantities not comparable should usually be in different formats: twelve 90-minute volumes or 12 ninety-minute volumes, not 12 90-minute volumes or twelve ninety-minute volumes.

• Avoid awkward juxtapositions: On April 28, 2006, thirty-one more died., not On April 28, 2006, 31 more died.

• Ages are typically stated in figures (8-year-old child) except for large, approximate values (69-million-year-old fossil).
• Sometimes figures and words carry different meanings; for example Every locker except one was searched implies there is a single exception (we don't know which), while Every locker except 1 was searched means that Locker 1 (only) was not searched.
• Proper names, technical terms, and the like are never altered:

The Sixth Sense;  5 Channel Street;  Channel 5;  Chanel No. 5;  Fourth Estate;  Third Reich;  Second Judicial District;  First Amendment;  Zero Hour; 

• Avoid beginning a sentence with figures:

  •   Not There were many attacks. 23 men were killed. but There were many attacks; 23 men were killed. or There were many attacks. Twenty-three men were killed.

  •   Not 1945 and 1950 saw crucial elections (nor Nineteen forty-five and 1950 saw crucial elections – because comparable numbers should be both written in words or both in figures) but The years 1945 and 1950 saw crucial elections or (better) The elections of 1945 and 1950 were crucial.

• Exception: Where a proper name, technical term, etc., itself beginning with a numeral, opens the sentence (1-Naphthylamine is typically synthesized via the Felden­shlager–Glocken­spiel process) although this can usually be avoided by rewording (Felden­shlager–Glocken­spiel is the process typically used in the synthesis of 1-Naphthylamine).

Ordinals

• Ordinal suffixes (st, nd, rd, th) are not superscripted (123rd and 496th, not 123^rd nor 496^th).
• Do not use a dot (.) or the ordinal mark (º) to indicate ordinals.

Fractions

• Spelled-out fractions are hyphenated: seven-eighths.
• Where numerator and denominator can each be expressed in one word, a fraction is usually spelled out (e.g. a two-thirds majority); use figures if they occur with an abbreviated unit (e.g. 1⁄4 yd—markup: {{frac|1|4}} yd, not a quarter of a yd or a quarter yd).
• Mixed numbers are usually given in figures, unspaced (not Fellini's film 8 1⁄2 or 8-1⁄2 but Fellini's film 81⁄2—markup: 8{{frac|1|2}}). In any case the integer and fractional parts should be consistent (not nine and 1⁄2).
• Metric (SI) measurements generally use decimals, not fractions (5.25 mm, not 51⁄4 mm).
• Non-metric (imperial and US customary) measurements may use fractions or decimals (51⁄4 inches; 5.25 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 11⁄3 times the original voltage, but 4/3 the original) and use of {{frac}} is discouraged in favor of one of these styles:

  •   $\textstyle {\frac {1}{2}}$  Markup: <math>\textstyle\frac{1}{2}</math>

  •   ⁠1/2⁠  Markup: {{sfrac|2}}

  •   1/2  Markup: 1/2

• Do not use special characters such as ½ (Markup (deprecated): ½ or ½).
• Ordinal suffixes such as th should not be used with fractions expressed in figures (not each US state has 1/50th of the Senate's votes, but one-fiftieth of the Senate's votes).
• Nouns following simple fractions are singular (He took 1⁄4 dose,  net change in score was −1⁄2 point,  3⁄2 dose).
• Nouns following mixed numbers are plural (victim knew even 11⁄2 doses could be fatal,  they sailed for 41⁄2 nautical miles).

Decimals

• A period/full stop (never a comma) is used as the decimal point (6.57, not 6,57).
• The number of decimal places should be consistent within a list or context (The response rates were 41.0 and 47.4 percent, respectively, not 41 and 47.4 percent), unless different precisions are actually intended.
• Numbers between −1 and +1 require a leading zero (0.02, not .02); exceptions are sporting performance averages (.430 batting average) and commonly used terms such as [[.22 caliber]].
• Nouns following a number expressed as a decimal are plural (averaging 0.7 years).
• Indicate repeating digits with an overbar e.g. 14.31{{overline|28}} gives 14.3128. (Consider explaining this notation on first use.) Do not write e.g. 14.31(28) because it resembles notations for § Uncertainty.

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): 12,200;   255,200;   8,274,527;   1,250 (optionally 1250).

• Exception: never group four-digit page numbers or four-digit calendar years (not sailed in 1,492, though 10,400 BC).
• In scientific/engineering articles, long strings left of the point may be grouped into triples: 8274527

• Right of the decimal point: Five or more digits may be grouped into triples separated by spaces: 99.123456.

• In mathematics-oriented articles, digits right of the point may be grouped into fives: 3.14159265358979323846....

Delimiting style should be consistent throughout a given article.

Markup: Templates {{val}}, {{val/delimitnum}} and {{gaps}} may be useful in grouping digits.

Percentages

• In the body of non-scientific articles, percent (American English) or per cent (British English) are commonly used: 10 percent; ten percent; 4.5 per cent. Ranges are written ten to twelve per cent or ten to twelve percent, not ten–twelve per cent or ten to twelve %.
• In the body of scientific/​technical articles, and in tables and infoboxes of any article, the symbol % (unspaced) is more common: 71%, not 71 % or three %. Ranges: 10–12%, not 10%–12% or 10 to 12%.
• When expressing the difference between two percentages, take care not to 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 60.22×10²², but 6.022×10²³.
• Engineering notation is similar, but adjusted so that the exponent is a multiple of three: 602.2×10²¹.
• Avoid mixing scientific and engineering notations (A 2.23×10² m² region covered by 234.0×10⁶ 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. × 10⁷ once in the column header, and omitting it in the individual entries. (Markup:× 10{{sup|7}})
• Either notation will distinguish the level of precision in a round number such as 5,000, which may mean 5×10³ (estimated to the nearest thousand), 5.0×10³ (to the nearest hundred), 5.00×10³ (to the nearest ten), or 5.000×10³ (to the unit).

Markup: {{Val}} and {{e}} 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:

  •  (1.534 ± 0.035) ×10²³ m 

  •  12.34 m² ± 5% (not used with scientific notation)

  •  15.34 ^+0.43
_−0.23 ×10²³ m 

  •  1.604(48) ×10⁻⁴ J (equivalent to (1.604±0.048)×10⁻⁴ J)

  •  Polls estimated Jones's share of the vote would be 55%, give or take about 3%

Markup: {{+-}}, {{su}}, and {{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 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.

  •   The speed of light is defined to be 299,792,458 m/s

but Particle velocities eventually reached almost two-thirds the 300 million m/s speed of light

  •   The city's 1920 population was 667,000. (not population was 666,666‍—‌an official figure unlikely to be accurate at full precision)

but 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.)

  •   The accident killed 337 passengers and crew, and three airport workers. (Likely that accurate and precise figures were determined.)

  •   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 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.)

  •   The jury's award was $8.5 million (where the actual figure was $8,462,247.63) – 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.

  •   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 {{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.

  •   The tallest player was 6 feet 3 inches (not ... about 6 feet 3 inches‍—‌heights are conventionally reported only to the nearest inch, even though greater precision may be available in principle).

but 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 (100,000 troops) as approximations. Writing a quantity in words (one hundred thousand troops) can further emphasize its approximate nature.

• See § Unit conversions below for precision issues when converting units.

Non-base-10 notations

• In computer-related articles, use the C programming language prefixes 0x (zero-ex) for hexadecimal and 0 (zero) for octal. For binary, use 0b. Explain these prefixes in the article's introduction or on first use.
• In all other articles, use <sub> to create subscripts: 137₉, 241₃. Markup: 137<sub>9</sub>, 241<sub>3</sub>
• For bases above 10 use symbols conventional for that base (as seen in reliable sources) e.g. for base 16 use 0–9A–F.

Units of 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 § Unit conversions below.

• In most articles, including all scientific articles, the main 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 angular speed, hands for heights of horses, etc.) Example: 44 kilograms (97 lb). The following exceptions apply:
• In non-scientific articles relating to the United States, the main units are US customary, e.g. 97 pounds (44 kg).
• In non-scientific articles relating to the United Kingdom, the main units for most quantities are metric or other internationally used units, except that:

• the main 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 main 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;
• 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: During metrification, the speed limit was changed from 30 miles per hour (48 kilometers/hour) to 50 km/h (31 mph).
• Nominal quantities (e.g. "2 × 4" lumber) require consideration of whether the article is concerned with the actual size of the item, or merely 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 § Unit conversions below). The {{convert}} template has a |disp=flip 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:

• Some examples of unit names: foot, meter, kilometer.
• Some 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. Up to 15 kilograms of filler is used for a batch of 250 kg).

• Certain unit names (e.g. °C) need never be written in full unless required stylistically (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–symbol pair (Energies were originally 2.3 megaelectronvolts (MeV) initally, but were eventually 6 MeV).
• Ranges use unspaced {{ndash}} if only one unit symbol is used at the end (e.g. 5.9–6.3 kg), and spaced en dash ({{snd}}) if two symbols are used (e.g. 3 μm – 1 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. from 5.9 to 6.3 kilograms, from 5.9 kilograms to 6.3 kilograms, from 5.9 to 6.3 kg and from 5.9 kg to 6.3 kg are all acceptable).
• Length–width, length–width–height and similar dimensions may be separated by the multiplication sign (×) or by.
  • With the multiplication sign, each number should be followed by a unit name or symbol (if appropriate):

  •  1 m × 3 m × 6 m or (1 × 3 × 6) m, not 1 × 3 × 6 m or 1 × 3 × 6 m³

  •  a metal plate 1 ft × 3 ft × 0.25 in

  •  a railroad easement 10 ft × 2.5 mi

• With by the unit need be given only once: 1 by 3 by 6 metres or 1 m by 3 m by 6 m
• The unspaced letter x may be used in common terms such as 4x4.

Unit names and symbols—General guidelines

Aspect	Guideline	Acceptable	Unacceptable
Spelling	The spelling of certain unit names (some of which are listed in § Specific units, below) varies with the variety of English followed by the article.
Format	Do not spell out numbers before unit symbols ...	5 min	five min
	... but words or numerals may be used with unit names.	five minutes 5 minutes
	Values not accompanied by units are usually given in figures.	Set the control to 10. These go to 11.	Set the control to ten. These go to eleven.
	Write unit names and symbols in upright roman type.	10 m 29 kilograms	10 m 29 kilograms
	Unit names are given in lower case except: where any word would be capital­ized; where otherwise specified in the SI brochure; where otherwise specified in this Manual of Style.	He walked several miles. Miles of trenches were dug.	A Gallon equals 4 Quarts.
	Except as listed in the "Specific units" table below, unit symbols are uncapi­tal­ized 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.	8 kg 100 kPa	8 Kg 100 kpa
	Unit symbols are undotted.	38 cm	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,   (or {{nowrap}} ) should be used to prevent linebreak.	29 kg Markup: 29 kg	29kg
	To form a value and a unit name into a compound adjective use a hyphen or hyphens ...	a five-day holiday a five-cubic-foot box a 10-centimeter blade
	... but a non-breaking space (never hyphen) separates a value and unit symbol.	a blade 10 cm long	a 10-cm blade
Plurals	SI unit names are pluralized by adding s or es...	1 ohm, 10 ohms
	... except for these irregular forms.	1 henry, 10 henries 1 hertz, 10 hertz 1 lux, 10 lux 1 siemens, 10 siemens	10 henrys 10 hertzes 10 luxes
	Some non-SI units have irregular plurals.	1 foot, 10 feet 1 stratum, 10 strata (unusual)	10 foots 10 stratums
	Unit symbols (in any system) are identical in singular and plural.	grew from 1 in to 2 in grew from 1 inch to 2 inches grew from one to two inches	grew from 1 in to 2 ins
Powers	Format exponents using <sup>, not special characters.	km2 Markup: km<sup>2</sup>	km² Markup: km&#178;
	Or use squared or cubed (after the unit being modified).	ten metres per second squared	ten metres per squared second
	For areas or volumes only, square or cubic may be used (before the unit being modified).		ten metres per square second
		grams per square centimeter
	The abbreviations sq and cu may be used for US customary and imperial units but not for SI units.	15 sq mi 3 cu ft	15 sq km 3 cu m
Products	Indicate a product of unit names with either a hyphen or a space.	foot-pound foot pound	footpound foot·pound
	Indicate a product of unit symbols with &middot; or &nbsp; (Note: {{middot}} is not equivalent to &middot;.)	ms = millisecond m·s or m s = metre-second.
	Exception: In some topic areas such as power engineer­ing, certain products take neither space nor &middot;. Follow the practice of reliable sources in the article's topic area.	Wh, VA, Ah kWh, MVA, GAh
	To pluralize a product of unit names, pluralize only the final unit. (Unit symbols are never pluralized.)	ten foot-pounds	ten feet-pounds
Ratios Rates Densities	Indicate a ratio of unit names with per.	meter per second	meter/second
	Indicate a ratio of unit symbols with a slash (followed by either a single symbol or a parenthesized product of symbols‍—‌do not use multiple slashes); or use −1, −2, etc.	metre per second m/s m·s−1	mps
		kg/(m·s)	kg/m/s kg/m·s
	To pluralize a ratio of unit names, pluralize only the "numerator" unit. (Unit symbols are never pluralized.)	ten newton-metres per second 10 N·m/s
	Some of the special forms used in the imperial and US customary systems are shown here ...	mph = miles per hour mpg = miles per gallon psi = pounds per square inch
	... but only the slash or negative exponent notations are used with SI (and other metric) units.	g/m2 g·m−2 km/h km·h-1	gsm kph
Prefixes	Prefixes should not be separated by a space or hyphen.	25 kilopascals	25 kilo pascals 25 kilo-pascals
	Prefixes are added without contraction, except as shown here:	kilohm megohm hectare	kiloohm megaohm hectoare
	centi-, deci-, deca-, and hecto- should be avoided; exceptions include centimetre, decibel, hectolitre, hectare, hectopascal.	100 metres 0.1 km	1 hectometre
	Do not use M for 103, MM for 106, or B for 109.	3 km 8 MW 125 GeV	3 Mm 8 MMW 125 BeV
Mixed units	Mixed units are traditionally used with the imperial and US customary systems …	1 ft 6 in 1 foot 6 inches 1.5 ft 18 in 1 US fl pt 8 oz
	... and in expressing time durations ...	1:30:07 1:30  1 hr 30 min 7 sec 1 h 30 m 7 s 1h 30m 07s	1 h 30 min 7 s 1 hr 30 m 7 sec 1:30′07″
	… but are not normally used in SI.	1.33 m 133 cm	1 m 33 cm
	No comma.	6 lb 3 oz	6 lb, 3 oz

Note to table:

Specific units

• The following table lists only units that need special attention.
• The SI standard should be consulted for guidance on use of other SI units. "Tables 6, 7, 8, and 9" give additional guidance on non-SI units.

Guidelines on specific units

Group	Name	Symbol	Comment
Length, Speed	inch	in	Do not use ′ (′), ″ (″), apostrophe/​single quote (') or double quote (")
	foot	ft
	foot per second	ft/s (not fps)
	hand	h or 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	kn (not kt or kN)
	metre meter (U.S.)	m
	micron	μm (not μ)	Markup: μm  Link to micrometre (for which micron is a synonym) on first use.
	mile	mi	In nautical and aeronautical contexts use statute mile rather than mile to avoid confusion with nautical mile.
	mile per hour	mph
	nautical mile	nmi or NM (not nm)
Volume, Flow	cubic centimetre cubic centimeter (U.S.)	cm3	Markup: cm<sup>3</sup>
		cc	Non-SI symbol used for certain engine displacements; link to cubic centimetre on first use.
	imperial fluid ounce	imp fl oz	US or imperial/imp must be specified; fluid/fl must be specified, except with gallon. (Without fluid, ounce is ambiguous – versus avoirdupois ounce or troy ounce – and pint or quart is ambiguous – versus US dry pint or US dry quart.)
	imperial fluid pint	imp fl pt
	imperial fluid quart	imp fl qt
	imperial gallon	imp gal
	US fluid ounce	US fl oz
	US fluid pint	US fl pt
	US fluid quart	US fl qt
	US gallon	US gal
	cubic foot	cu ft (not cf)	Write five million cu ft or 5,000,000 cu ft, not 5 MCF.
	cubic foot per second	cu ft/s (not cfs)
	litre liter (U.S.)	l or L	The symbol l in isolation (i.e. not in such forms as ml) is easily mistaken for the digit 1.
Mass, Force, Density, Pressure	long ton	long ton	Spell out in full.
	short ton	short ton
	pound per square inch	psi
	tonne metric ton (U.S.)	t (not mt or MT)
	troy ounce	oz t	t or troy must be specified. Articles about precious metals, black powder, and gemstones should always specify whether ounces and pounds are avoirdupois or troy.
	troy pound	lb t or troy
	carat	carat	Used to express masses of gemstones and pearls.
Purity	carat or karat	k or Kt	A measure of purity for gold alloys. (Do not confuse with the unit of mass with the same spelling.)
Time	second	s	Do not use &prime; (′), &Prime; (″), apostrophe (') or quote (") for minutes or seconds. Use m for minute only where there is no danger of confusion with meter, as in the hours–minutes–seconds formats for time durations described in the Unit names and symbols table.
	minute	min
	hour	h
	year	a	Use a only with an SI prefix (a rock formation 540 Ma old, not Life expectancy rose to 60 a).
		y or yr
Information	bit	bit (not b or B)	See also § Quantities of bytes and bits, below.
	byte	B or byte (not b or o)
	bit per second	bit/s (not bps)
	byte per second	B/s or byte/s (not Bps or Bps)
Angle
	arcminute	′	Markup: &prime;  (not apostrophe/​single quote '). No space between numerals and symbol (47′, not 47 ′)
	arcsecond	″	Markup: &Prime;  (not double-quote "). No space between numerals and symbol (22″, not 22 ″)
	degree	°	Markup: &deg;  (not masculine ordinal º or ring ̊ ). No space between numerals and symbol (23°, not 23 °)
Temperature	degree		Markup: &deg;. Nonbreaking space ({{nbsp}}) between numerals and symbol (40 °, not 40°; 12 °C, not 12°C, nor 12° C)
	degree Celsius (not degree centigrade)	°C (not C)
Energy	gram calorie small calorie	cal	In certain subject areas calorie is convention­ally 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 (kcal); other SI prefixes may be used with the gram calorie (e.g., Mcal) but not with the kilogram calorie (do not use kCal or MCal).
	kilogram calorie large calorie (not Calorie)	Cal

Quantities of bytes and bits

In quantities of bits and bytes, 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 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 k should be used for "kilo-" whenever it means 1000 in computing contexts, whereas a capital 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 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 ({{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 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:

  •  A 64 MB (64 × 1024²-byte) video card and a 100 GB (100 × 1000³-byte) hard drive

  •  A 64 MB (64 × 2²⁰-byte) video card and a 100 GB (100 × 10⁹-byte) hard drive

  •  A 64 MB (67,108,864-byte) video card and a 100 GB (100,000,000,000-byte) hard drive

• Avoid inconsistent combinations such as A 64 MB (67,108,864-byte) video card and a 100 GB (100 × 1000³-byte) hard drive. Footnotes, such as those seen in Power Macintosh 5500, may be used for disambiguation.
• Unless explicitly stated otherwise, one byte is eight bits (see History of byte).

The IEC prefixes kibi-, mebi-, gibi-, etc. (symbols Ki, Mi, Gi, etc.) are rarely used, even in technical articles, so 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,
• 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

Where English-speaking countries use different units for the same quantity, follow the "primary" quantity with a conversion in parentheses: the Mississippi River is 2,320 miles (3,734 km) long; the Murray River is 2,375 kilometres (1,476 mi) 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 US customary system, or vice-versa‍—‌and in particular, where those systems give a single term different definitions‍—‌a double conversion may be appropriate: Rosie weighed 19 stone (266 lb; 121 kg), The car had a fuel economy of 5 L/100 km (47 mpg_‑US; 56 mpg_‑imp)
• 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 (The four-minute mile).
  • When units are part of the subject of a topic‍—‌nautical miles in articles about the history of nautical law (5 nautical miles), SI units in scientific articles (a 600-kilometer asteroid), yards in articles about American football‍—‌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 the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). Small numbers may need to be converted to a range where rounding would cause a significant distortion, so one mile (1–2 km), not one mile (2 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.
• Conversion templates can be used to convert and format many common units, including {{convert}}, which includes non-breaking spaces.
• In a direct quotation, always keep the source units. Any required conversions can be added, in the quote in square brackets after the original measurement, or in a footnote. See footnoting and citing sources.
• {{Units_attention}} may be added to articles needing general attention regarding choice of units and unit conversions.

Currencies and monetary values

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 ($123), euros (€123), or pounds sterling (£123).

Currency names

• Do not capitalize the names of currencies, currency subdivisions, coins and banknotes except e.g. at the start of a sentence.
• To pluralize euro use the standard English plurals (ten euros and fifty cents), not the invariant plurals used for European Union legislation and banknotes ( ten euro and fifty cent). For the adjectival form, use a hyphenated singular: (a two-euro pen;   a ten-cent coin).
• Link the first occurrence of lesser-known currencies (Mongolian tögrögs).

Currency symbols

• In general, the first mention of a particular currency should use its full, unambiguous signifier (e.g. A$52), with subsequent references using just the appropriate symbol (e.g. $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 – see Currency symbols § dollar variants) use the full signifier (e.g. US$, A$) 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 (€26, £22 or $34), 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. See also List of circulating currencies.

Format

• A period (full stop) is used as the decimal point‍—‌never a comma ($6.57, not $6,57).
• For grouping of digits (e.g. £1,234,567) see § Grouping of digits, above.
• Do not place the currency symbol after the accompanying numeric figures (e.g. 123$, 123£, 123€) unless that is the normal convention for that currency when writing in English. Never use forms such as $US123 or $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 (£123;   €123); but spaced if alphabetic (R 75).
• Ranges should be expressed giving the currency signifier just once: $250–300, not $250–$300.
• million and billion should be spelled out on first use, and (optionally) abbreviated M or bn (both unspaced) thereafter: She received £70 million and her son £10M; the school's share was $250–300 million, and the charity's $400–450M.
• In general, a currency symbol should be accompanied by a numeric amount e.g. not He converted his US$ to A$ but He converted his US dollars to Australian dollars or He exchanged the US$100 note for Australian dollars.

• Exceptions may occur in tables and infoboxes where space is limited e.g. Currencies accepted for deposit: US$, SFr, GB£, €. 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—‌such as the US dollar, euro or pound sterling‍—‌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. Since 2001 the grant has been 10,000,000 Swedish kronor ($1.4M, €1.0M, or £800k as of August 2009), not ($1,390,570, €971,673 or £848,646).
• 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 {{Inflation}} and {{Inflation-fn}}.

Common mathematical symbols

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 two operands, but no space with one operand
• The {{nbsp}} and {{nobreak}} templates may be useful in preventing awkward linebreaks in mathematical material.

Common mathematical symbols

Symbol name	Example	Markup	Comments
Plus / positive	x + y	''x'' + ''y''
	+y	+''y''
Minus / negative	x − y	''x'' − ''y''	Do not use hyphen (-) or dashes ({{ndash}} or {{mdash}}).
	−y	−''y''
Plus-minus / minus-plus	41.5 ± 0.3	41.5 ± 0.3
	−(±a) = ∓a	−(±''a'') = ∓''a''
Multiplication, cross	x × y	''x'' × ''y''	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, obelus	x ÷ y	''x'' ÷ ''y''
Equal / equals	x = y	''x'' = ''y''
Not equal	x ≠ y	''x'' ≠ ''y''
Approx. equal	π ≈ 3.14	{{pi}} ≈ 3.14
Less than	x < y	''x'' &lt; ''y''
L.T. or equal	x ≤ y	''x'' &le; ''y''
Greater than	x > y	''x'' &gt; ''y''
G.T. or equal	x ≥ y	''x'' &ge; ''y''

Geographical coordinates

For draft guidance on, and examples of, coordinates for linear features, see Wikipedia:WikiProject Geographical coordinates/Linear.

Quick guide:

Quick how-to

To add 57°18′22″N 4°27′32″W to the top of an article, use {{Coord}}, thus:

{{Coord|57|18|22|N|4|27|32|W|display=title}}

These coordinates are in degrees, minutes, and seconds of arc.

"title" means that the coordinates will be displayed next to the article's title at the top of the page (in desktop view only; title coordinates do not display in mobile view) and before any other text or images. It also records the coordinates as the primary location of the page's subject in Wikipedia's geosearch API.

To add 44.1124°N 87.9130°W / 44.1124; -87.9130 to the top of an article, use either

{{Coord|44.1124|N|87.9130|W|display=title}}

(which does not require minutes or seconds but does require the user to specify north/ south and east/west) or

{{Coord|44.1124|-87.9130|display=title}}

(in which the north and east are presumed by positive values while the south and west are negative ones). These coordinates are in decimal degrees.

• Degrees, minutes and seconds, when used, must each be separated by a pipe ("|").
• Map datum must be WGS84 if possible (except for off-Earth bodies).
• Avoid excessive precision (0.0001° is <11 m, 1″ is <31 m).
• Maintain consistency of decimal places or minutes/seconds between latitude and longitude.
• Latitude (N/S) must appear before longitude (E/W).

Optional coordinate parameters follow the longitude and are separated by an underscore ("_"):

• dim: dim:N (viewing diameter in metres)
• region: region:R (ISO 3166-1 alpha-2 or ISO 3166-2 code)
• type: type:T (landmark or city(30,000), for example)

Other optional parameters are separated by a pipe ("|"):

• display

  |display=inline (the default) to display in the body of the article only,

  |display=title to display at the top of the article only (in desktop view only; title coordinates do not display in mobile view), or

  |display=inline,title to display in both places.

• name

  name=X to label the place on maps (default is PAGENAME)

Thus: {{Coord|44.1172|-87.9135|dim:30_region:US-WI_type:event

|display=inline,title|name=accident site}}

Use |display=title (or |display=inline,title) once per article, for the subject of the article, where appropriate.

• Per WP:ORDER, the template is placed at the bottom of the article in the 'end matter', after any navigation templates, but before all categories, including the {{DEFAULTSORT}} template. The {{coord}} template may also be placed within an infobox, instead of at the bottom of the article.
• For full details, refer to {{Coord/doc}}.
• Additional guidance is available at obtaining coordinates and converting coordinates.

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.

Two types of template are available:

• {{coord}} offers users a choice of display format through user styles, 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 {{Infobox settlement}}, which automatically emit {{Coord}}.

The following formats are available.

• For degrees only (including decimal values): {{coord|dd|N/S|dd|E/W}}
• For degrees/minutes: {{coord|dd|mm|N/S|dd|mm|E/W}}
• For degrees/minutes/seconds: {{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• dd, mm, ss are the degrees, minutes and seconds, respectively;
• N/S is either N for northern or S for southern latitudes;
• E/W 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:

The city of Oslo, located at 59° 55′ N, 10° 44′ E, enter:

{{coord|59|55|N|10|44|E}}‍—‌which becomes 59°55′N 10°44′E

For a country, like Botswana, less precision is appropriate:

{{coord|22|S|24|E}}‍—‌which becomes 22°S 24°E

Higher levels of precision are obtained by using seconds:

{{coord|33|56|24|N|118|24|00|W}}‍—‌which becomes 33°56′24″N 118°24′00″W

Coordinates can be entered as decimal values

{{coord|33.94|S|118.40|W}}‍—‌which becomes 33.94°S 118.40°W / -33.94; -118.40

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 less precise the coordinates should be. For example, if just giving the location of a city, precision greater than 100 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 meters or even one meter in some cases (1′′ ~15 m to 30 m, 0.0001° ~5.6 m to 10 m).

The final field, following the E/W, is available for attributes such as type, region and scale.

When adding coordinates, please remove the {{coord missing}} tag from the article, if present.

For more information, see the geographical coordinates WikiProject.

Templates other than {{coord}} should use the following variable names for coordinates: lat_d, lat_m, lat_s, lat_NS, long_d, long_m, long_s, long_EW.

See also

• Wikipedia:Naming conventions (numbers and dates)
• Wikipedia:Date formattings
• m:Help:Date formatting feature at Meta
• m:Help:Calculation § Displaying numbers and numeric expressions at Meta