Wikipedia:Manual of Style/Dates and numbers

"WP:DATE" redirects here. For the other guideline, see Wikipedia:Avoid statements that will date quickly.

This part of the Manual of Style aims to achieve consistency in the use and formatting of dates and numbers in Wikipedia articles. Consistent standards make articles easier to read, write and edit. Where this manual provides options, consistency should be maintained within an article, unless there is a good reason to do otherwise. In direct quotations, the original text should be preserved.

In June 2005, the Arbitration Committee ruled that when either of two styles is acceptable, it is inappropriate for an editor to change an article from one style to another unless there is a substantial reason to do so. Edit warring over optional styles is unacceptable. If an article has been stable in a given style, it should not be converted without a style-independent reason. Where in doubt, defer to the style used by the first major contributor.

Non-breaking spaces

• In compound items in which numerical and non-numerical elements are separated by a space, a non-breaking space (or hard space) is recommended to avoid the displacement of those elements at the end of a line.
• With page numbers, p. or pp. should be followed by a non-breaking space. Similarly for related numbers (like series, volume, section), in citations and in text.
• A non-breaking space can be produced with the HTML code   instead of the space bar: 19 kg yields a non-breaking 19 kg.
• A non-breaking space can also be produced by using the {{nowrap}} template: {{nowrap|8 sq ft}} produces a non-breaking 8 sq ft. This is especially useful for short constructions requiring two or more non-breaking spaces, as in the preceding example.
• In some older browsers, quotation marks separated by a non-breaking space may still be broken at the end of a line: ("She said 'Yes!' ").
• Unlike normal spaces, multiple non-breaking spaces are not compressed by browsers into a single space.

Chronological items

Precise language

Avoid statements that will date quickly, except on pages that are regularly updated, such as those that cover current events. Avoid such items as recently and soon (unless their meaning is clear in a storyline), currently (except on rare occasions when it is not redundant), and is soon to be superseded. Instead, use either:

• more precise items (since the start of 2005; during the 1990s; is expected to be superseded by 2008); or
• an as of phrase (as of August 2007), which is a signal to readers of the time-dependence of the statement, and to later editors of the need to update the statement (see As of).

Times

Context determines whether the 12- or 24-hour clock is used; in both, colons separate hours, minutes and seconds (1:38:09 pm and 13:38:09).

• 12-hour clock times end with dotted or undotted lower-case a.m. or p.m., or am or pm, which are spaced (2:30 p.m. or 2:30 pm, not 2:30p.m. or 2:30pm). Noon and midnight are used 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 this is clear from the context.
• 24-hour clock times have no a.m., p.m., noon or midnight suffix. Discretion may be used as to whether the hour has a leading zero (08:15 or 8:15). 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.

Dates

• Wikipedia does not use ordinal suffixes or articles, or put a comma between month and year.

Incorrect	February 14th, 14th February, the 14th of February
Correct	14 February, February 14
Incorrect	October, 1976
Correct	October 1976

• Date ranges are preferably given with minimal repetition (5–7 January 1979; September 21–29, 2002), using an unspaced en dash. If the autoformatting function is used, the opening and closing dates of the range must be given in full (see Autoformatting and linking) and be separated by a spaced en dash.
• Rarely, a night may be expressed in terms of the two contiguous dates using a slash (the bombing raids of the night of 30/31 May 1942); this cannot be done using the autoformatting function.
• Yearless dates (5 March, March 5) are inappropriate unless the year is obvious from the context. There is no such ambiguity with recurring events, such as "January 1 is New Year's Day".
• ISO 8601 dates (1976-05-12) are uncommon in English prose, and are generally not used in Wikipedia. However, they may be useful in long lists and tables for conciseness and ease of comparison.

Full date formatting

In general, the following formats are acceptable:

• International format: 14 February and 14 February 1991 (more common in many countries);
• American format: February 14 and February 14, 1990 (more common in the US).

Disputes between editors over date formats are avoided by using three simple guidelines. See also autoformatting and linking.

Consistency within articles

• The same format should be used in the main text, footnotes and references of each article, except for:
  • dates within quotations and titles, where the original format is retained;
  • explicit comparisons of date formatting.

Strong national ties to a topic

Articles on topics with strong ties to a particular English-speaking nation should generally use the more common date format for that nation; articles related to Canada may use either format consistently. Articles related to other countries that commonly use one of the two acceptable guidelines above should use that format.

Retaining the existing format

• If an article has evolved using predominantly one format, the whole article should conform to that variety, unless there are reasons for changing it on the basis of strong national ties to the topic.
• In the early stages of writing an article, the format chosen by the first major contributor to the article should be used, unless there is reason to change it on the basis of strong national ties to the topic. Where an article that is not a stub shows no clear sign of which format is used, the first person to insert a date is equivalent to the first major contributor.

Dates of birth and death

At the start of an article on a person, his or her dates of birth and death are provided. For example: "Charles Darwin (12 February 1809 – 19 April 1882) was a British ..."

• Locations of birth and death are given subsequently rather than being entangled with the dates.
• When only the years are known: "Socrates (470–399 BC) was ..."
• For a person still living: "Serena Williams (born September 26 1981) ...", not "... (September 26 1981–) ..."
• When the date of birth is unknown: "Offa (died 26 July 796) ..."
• When the date of birth is known only approximately: "Genghis Khan (c. 1162 – August 18, 1227) ..."
• When the dates of both birth and death are known only approximately: "Dionysius Exiguus (c. 470 – c. 540) ..."
• When the date of death is unknown, but the person is certainly now dead: "Robert Menli Lyon (born 1789, date of death unknown) ..."
• When only the dates of the person's reign are known, and only approximately: "Rameses III (reigned c. 1180 BCE – c. 1150 BCE) ..."
• When the person is known to have been alive (flourishing) at certain dates, [[floruit|fl.]] is used to link to floruit, in case the meaning is not familiar: "Osmund (fl. 760–72) ..."
• When the person is known to have been alive as early as about 660, and to have died in 685: "Aethelwalh (fl. c. 660–85) ..."

In biographical infobox templates, provide age calculation with {{birth date and age}} for living people and {{death date and age}} for the deceased when the full birth or death date, respectively, is known.

Other date ranges

Dates that are given as ranges should follow the same patterns as given above for birth and death dates. Ranges that come up to the present (as of the time that the information was added to the article) should generally be given in ways that prevent their becoming counterfactually obsolete, e.g. from 1996 onward (as of October 2007), not from 1996 to the present; "the present" is a constantly moving target. In the main text of articles, the form 1996– (with no date after the en-dash) should not be used, though it is preferred in infoboxes and other crowded templates or lists, with the caveat that they may need to be examined by editors more frequently to see if they need to be updated; it is helpful to other editors to add an HTML comment immediately after such constructions, giving the as-of date, e.g.: <!--as of 10 October 2007-->. The form since 1996' should be used in favor of 1996–present in article text and infoboxes.

Longer periods

• Months are expressed as whole words (February, not 2), except in the ISO 8601 format. Abbreviations such as Feb are used only where space is extremely limited, such as in tables and infoboxes. Do not insert of between a month and a year (April 2000, not April of 2000).

• Seasons. Because the seasons are not simply reversed in each hemisphere— and areas near the equator tend to have just wet and dry seasons—neutral wording may be preferable (in early 1990, in the second quarter of 2003, around September). Use a date or month rather than a season name, unless there is a logical connection (the autumn harvest). Seasons are normally spelled with a lower-case initial.
• Years

• Years are normally expressed in digits; a comma is not used in four-digit years (1988, not 1,988).
• Avoid inserting the words the year before the digits (1995, not the year 1995), unless the meaning would otherwise be unclear.
• Either CE and BCE or AD and BC can be used—spaced, undotted (without periods) and upper-case. Choose either the BC/AD or the BCE/CE system, but not both in the same article. AD appears before a year (AD 1066) but after a century (2nd century AD); the other abbreviations appear after (1066 CE, 3700 BCE, 3700 BC). The absence of such an abbreviation indicates the default, CE/AD. It is inappropriate for a Wikipedia editor to change from one style to another unless there is a substantive reason; the Manual of Style favors neither system over the other

• Uncalibrated (bce) radiocarbon dates: 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], 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 recognize the distinction between bce and BCE / BC.

• Year ranges, like all ranges, are separated by an en dash (do not use a hyphen or slash (2005–08, not 2005-08 or 2005/08)). A closing CE/AD year is normally written with two digits (1881–86) unless it is in a different century from that of the opening year (1881–1986). The full closing year is acceptable, but abbreviating it to a single digit (1881–6) or three digits (1881–886) is not. A closing BCE or BC year is given in full (2590–2550 BCE). While one era signifier at the end of a date range requires an unspaced en dash (12–5 BC), a spaced en dash is required when a signifier is used after the opening and closing years (5 BC – AD 29).
• A slash may be used to indicate regular defined yearly periods that do not coincide with calendar years (the financial year 1993/94).
• Abbreviations indicating long periods of time ago—such as BP (before present), as well as various annum-based units such as Ka (kiloannum) and kya (thousand years ago), Ma (megaannum) and mya (million years ago), and Ga (gigaannum or billion years ago)—are given as full words and wikilinked on first occurrence.

• BP: Do not convert other notations to BP unless you are certain of what you are doing. In some contexts the unit BP is actually defined as "years before 1950 CE/AD", not "years before the literal present", and the conversion may introduce an error if the date being converted is not a wide approximation (18,000 BP) but a more narrow one or an actual known year. 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, etc.)

• To indicate around/approximately/about), the abbreviations c. and ca. are preferred over circa, approximately or approx., and are spaced (c. 1291). Do not use a question mark for this function (1291?), as this may indicate to the reader an uncertainty on the part of Wikipedia editors rather than on the part of reliable historians.

• Decades contain no apostrophe (the 1980s, not the 1980’s); the two-digit form is used only where the century is clear (the ’80s or the 80s).
• Centuries and millennia

• There was no year 0. Thus, the first century CE was AD 1–100, the 17th century AD was 1601–1700 CE, and the second millennium AD/CE was 1001–2000; the first century BCE was 100–1 BC; the 17th century BC was 1700–1601 BCE, and the second millennium BCE was 2000–1001 BC.
• Use numerals for centuries (the 17th century); do not capitalize century.
• The 1700s refers to a decade, not a century, that is, 1700-1710, not 1700-1799.

Calendars

See also: Old Style and New Style dates

Dates can be given in any appropriate calendar, as long as the date in either the Julian or Gregorian calendars is provided, 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, this must be clear to readers.

• Current events are given in the Gregorian calendar.
• Dates before the adoption of the Gregorian calendar on 1582-10-15 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.
• The Julian or Gregorian equivalent of dates in early Egyptian and Mesopotamian history is often debatable. Follow the consensus of reliable sources, or indicate their divergence.
• Dates of events in countries using the Gregorian calendar are given in the Gregorian calendar. This includes some of the Continent of Europe from 1582, the British Empire from 1752-09-14, and Russia from 1918-02-14 (see the Gregorian calendar article).

The dating method used in a Wikipedia article should follow that used by reliable secondary sources. If the reliable secondary sources disagree, choose the most common used by reliable secondary sources and note the usage in a footnote.

At some places and times, dates other than 1 January were used as the start of the year. The most common English-language convention is the Annunciation Style used in Britain and its colonies, in which the year started on 25 March, Annunciation Day; see the New Year article for a list of other styles. 1 January is assumed to be the opening date for years; if there is reason to use another start-date, this should be stated.

If there is a need to mention Old Style 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).

Time zones

When writing a date, first consider where the event happened and use the time zone there. For example, the date of the Attack on Pearl Harbor should be December 7, 1941 (Hawaii time/date). If it is difficult to judge where, consider what is significant. For example, if a vandal based in Japan attacked a Pentagon computer in the United States, use the time zone for the Pentagon, where the attack had its effect. If known, include the UTC date and time of the event in the article, indicating that it is UTC.

Autoformatting and linking

• Full dates, and days and months, are normally autoformatted by inserting double square-brackets, as for linking. This instructs the MediaWiki software to format the item according to the date preferences chosen by registered users. It works only for users who are registered, and for all others (i.e. most) will be displayed as entered. Thus:
  • either [[January 15]] or [[15 January]] will be rendered as either January 15 or 15 January, according to a registered user's set preferences; and
  • [[January 15]], [[2001]] (US editors), [[15 January]] [[2001]] (others), [[2001-01-15]] (ISO), or [[2001 January 15]] will be rendered as January 15, 2001, 15 January 2001, 2001-01-15, or 2001 January 15, according to a registered user's set preferences.
• Do not autoformat dates that are:
  • in article and section headings,
  • on disambiguation pages,
  • within quotations (unless the original text was wikilinked).
  • in date ranges within the same calendar month. The autoformatting mechanism does not work correctly with date ranges (December 13–17, 1951) or slashes (the night of 30/31 May).
• Wikipedia has articles on days of the year, years, decades, centuries and millennia. Link to one of these pages only if it is likely to deepen readers' understanding of a topic. Piped links to pages that are more focused on a topic are possible ([[1997 in South African sport|1997]]), but cannot be used in full dates, where they break the date-linking function.

Numbers

Spelling out numbers

General rule

• In the body of an article, single-digit whole numbers (from zero to nine) are spelled out; numbers of more than one digit are generally rendered as digits, but may be spelled out if they are expressed in one or two words (sixteen, eighty-four, two hundred and 3.75, 544, 21 million).

Exceptions

• Numbers in mathematical formulas are never spelled out (3 < π < 22/7, not three < π < 22 sevenths).
• The numerical elements of dates and times are not normally spelled out (that is, do not use the seventh of January or twelve forty-five p.m.). Spell them out in historical references, such as Seventh of March speech and Fifth of November.
• Numbers that open a sentence are spelled out; alternatively, the sentence can be recast so that the number is not in first position.
• In tables and infoboxes, all numbers are expressed as numerals when offered as data. Numbers within a table's expounding text and comments should be consistent with the general rule.
• Within a context or a list, style should be consistent (either 5 cats and 32 dogs or five cats and thirty-two dogs, not five cats and 32 dogs).
• On rare occasions when digits may cause confusion, spell out the number (thirty-six 6.4-inch rifled guns, not 36 6.4-inch rifled guns).
• Fractions are normally spelled out; use the fraction form if they occur in a percentage or with an abbreviated unit (⅛ mm, but never an eighth of a mm) or they are mixed with whole numerals.
• Decimal representations containing a decimal point are not spelled out (1.00, 3.14159).
• A small whole number in a percentage may be spelled out, but only if the percent sign is not used (three percent or 3%, not three %). If in a context some percentages are presented with numerals, then all are to be presented that way.
• Ordinal numbers are spelled out using the same rules as for cardinal numbers. The exception is ordinals for centuries, which are expressed in digits (the 5th century CE; 19th-century painting). The ordinal suffix (e.g., th) is not superscripted (23rd and 496th, not 23^rd and 496^th). Spell out ordinal numbers when they are inclusive used as the first word of a proper name (e.g. Fourth Amendment; Seventeenth Judicial District).
• Proper names and formal numerical designations comply with common usage (Chanel No. 5, 4 Main Street, 1-Naphthylamine, Channel 6). This is the case even where it causes a numeral to open a sentence, although this is usually avoided by rewording.
• The numeral and the spelled-out number can have different meanings, as in these two phrases:
  • Every number except one, in which one refers to the number of exceptions (for example, the one exception could be the number 42), although rephrasing to avoid the ambiguity would be better; and
  • Every number except 1, in which the specific number 1 is the exception (this usage is not ambiguous).

Hyphenation

• Spelled-out two-word numbers from 21 to 99 are hyphenated (fifty-six), as are fractions (seven-eighths). Do not hyphenate other multi-word numbers (five hundred, not five-hundred).

Large numbers

See also Magnitude prefixes, Order of magnitude and Long and short scales.

• Commas are used to break the sequence every three places left of the decimal point; spaces or dots are never used in this role (2,900,000, not 2 900 000).
• Large rounded numbers are generally assumed to be approximations; only where the approximation could be misleading is it necessary to qualify with about or a similar term.
• Avoid overly precise values where they are unlikely to be stable or accurate, or where the precision is unnecessary in the context (The speed of light in a vacuum is 299,792,458 metres per second is probably appropriate, but The distance from the Earth to the Sun is 149,014,769 kilometres and The population of Cape Town is 2,968,790 would usually not be, because both values are unstable at that level of precision, and readers are unlikely to care in the context.)
• Scientific notation (5.8 × 10⁷) is preferred in scientific contexts.
• Where values in the millions occur a number of times through an article, upper-case M may be used for million, unspaced, after spelling out the first occurrence. (She bequeathed her fortune of £100 million unequally: her eldest daughter received £70M, her husband £18M, and her three sons each just £4M each.)
• Billion is understood as 10⁹. After the first occurrence in an article, billion may be abbreviated to unspaced bn ($35bn). Where the alternative meaning 10¹² is required for some reason, a footnote or inline comment is appropriate. Except in computing and certain scientific contexts, giga- or its symbol G is inappropriate.

Decimal points

• A decimal point is used between the integer and the fractional parts of a decimal; a comma is never used in this role (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 The response rates were 41 and 47.4 percent, respectively).
• Numbers between minus one and plus one require a leading zero (0.02, not .02); exceptions are sporting performance averages (.43 batting average) and commonly used terms such as .22 caliber.

Percentages

• Percent or per cent are commonly used to indicate percentages in the body of an article. The symbol % is more common in scientific or technical articles and in complex listings.
• The symbol is unspaced (71%, not 71 %).
• In tables and infoboxes, the symbol % is normally preferred to the spelled-out percent or per cent.
• Ranges are preferably formatted with one rather than two percentage signifiers (22–28%, not 22%–28%).
• Avoid ambiguity in expressing a change of rates. This can be done by using percentage points, not percentages, to express a change in a percentage or the difference between two percentages; for example, "The agent raised the commission by five percentage points, from 10 to 15%" (if the 10% commission had instead been raised by 5%, the new rate would have been 10.5%). It is often possible to recast the sentence to avoid the ambiguity ("made the commission larger by half."). Percentage point should not be confused with basis point, which is a hundredth of a percentage point.

Natural numbers

The set of natural numbers has two common meanings: {0,1,2,3,…}, which may also be called non-negative integers, and {1,2,3,…}, which may also be called positive integers. Use the sense appropriate to the field to which the subject of the article belongs if the field has a preferred convention. If the sense is unclear, and if it is important whether or not zero is included, consider using one of the alternative phrases rather than natural numbers if the context permits.

Non-base-10 notations

For numbers expressed in bases other than base ten:

• In computer-related articles, use the C programming language prefixes 0x (zero-ex) for hexadecimal and 0 (zero) for octal. For binary, use 0b. Consider including a note at the top of the page about these prefixes.
• In all other articles, use subscript notation. For example: 137₉, 241₆, 2A9₁₂, A87D₁₆ (use <sub> and </sub>).
• For base eleven and higher, use whatever symbols are conventional for that base. One quite common convention, especially for base 16, is to use upper-case A–Z for digits from 10 up to 35 (0x5AB3).

Units of measurement

Which system to use

• For US-related articles, the main units are US units; for example, 23 miles (37 km).
• For UK-related, the main units are either metric or imperial (consistently within an article).
• For other country-related articles, the main units are metric; for example, 37 kilometres (23 mi).
• American English spells metric units with final -er (kilometer); in all other varieties of English, including Canadian English, -re is used (kilometre).
• In scientific articles, use the units employed in the current scientific literature on that topic. This will usually be SI, but not always; for example, natural units are often used in relativistic and quantum physics, and Hubble's constant should be quoted in its most common unit of (km/s)/Mpc rather than its SI unit of s⁻¹.
• If editors cannot agree on the sequence of units, put the source value first and the converted value second. If the choice of units is arbitrary, use SI units as the main unit, with converted units in parentheses.

Conversions

• Conversions to and from metric and US units are generally provided. There are exceptions, including:
  • articles on scientific topics where there is consensus among the contributors not to convert the metric units, in which case the first occurrence of each unit should be linked;
  • where inserting a conversion would make a common expression awkward (the four-minute mile).
  • in topics such as the history of maritime law in which imperial units (for example, miles and nautical miles) are part of the subject, it is useful to provide metric conversions, but excessive to convert exactly the same unit and value every time it occurs.
• In the main text, spell out the main units and use unit symbols or abbreviations for conversions in parentheses; for example, a pipe 100 millimetres (4 in) in diameter and 16 kilometres (10 mi) long or a pipe 4 inches (100 mm) in diameter and 10 miles (16 km) long. The exception is that where there is consensus to do so, the main units may also be abbreviated in the main text after the first occurrence.
• Converted values should use a level of precision similar to that of the source value; for example, the Moon is 380,000 kilometres (240,000 mi) from Earth, not ... (236,121 mi).
• {{Convert}} or unit-specific templates from Category:Conversion templates can be used to convert and format many common units in accordance with this manual of style.
• In a direct quotation:
  • conversions required for units cited within direct quotations should appear within square brackets in the quote;
  • if the text contains an obscure use of units (e.g., five million board feet of lumber), annotate it with a footnote that provides standard modern units, rather than changing the text of the quotation.
• Measurements should be accompanied by a proper citation of the source using a method described at the style guide for citation.
• Where footnoting or citing sources for values and units, identify both the source and the original units.

Unit symbols and abbreviations

• In accordance with the rules of CGPM, NIST, National Physical Laboratory (UK), unit symbols are never italicized, but always in upright type.
• Standard abbreviations and symbols for units are undotted. For example, m for meter and kg for kilogram (not m. or kg.), in for inch (not in., " or ″), ft for foot (not ft., ' or ′) and lb for pound (not lb. or #).
• When spelled-out unit names are combined by multiplication, separate them with a space (newton meter).
• When units are combined by multiplication, use a middle dot to separate them (e.g., for newton metre, use the symbol N·m, not Nm, N-m, N m or N•m).
• The degree symbol is °. Using any other symbol (e.g. masculine ordinal º or "ring above" ˚) for this purpose is incorrect.
• The symbol for the bit is 'bit'. The byte may be represented by either one of the symbols ‘B’ and ‘byte’. Unless explicitly stated otherwise, one byte is eight bits (1 B = 8 bit), and no 's' is added to either symbol in the case of a plural. Decimal or binary prefix symbols may be added to either unit symbol. Thus
  • the quantity one kilobit is represented by 1 kbit (and not 1 kb), the quantity eight megabits is represented by 8 Mbit (and not 8 Mb or 8 Mbits);
  • the quantity ten megabytes is represented by either 10 MB or 10 Mbyte (and not 10 Mb or 10 Mbytes).
• Do not append an s for the plurals of unit symbols (kg, km, in, lb, not kgs, kms, ins, lbs).
• Temperatures are always accompanied by °C for degrees Celsius, °F for degrees Fahrenheit, or K for kelvins (35 °C, 5,000 K); these three symbols are always upper-case. For the first two, the unit is a degree; for the last, it is now normally the SI kelvin rather than degree Kelvin (i.e. do not use 5,000 °K)
• Avoid the use of unit abbreviations that have conflicting meanings in common units systems such as SI and US customary units:
  • Use nmi (or NM) to abbreviate nautical mile rather than nm;
  • Use kn to abbreviate knot rather than kt or kts;
  • Link such units to their definitions on first use.
• Values and unit symbols are spaced (25 kg, not 25kg). The exceptions are degrees, minutes and seconds for angles and coordinates (the coordinate is 5° 24′ 21.12″ N, the pathways are at a 180° angle, but the average temperature is 18 °C).
• Squared and cubic metric-symbols are always expressed with a superscript exponent (5 km²); squared US-unit abbreviations are rendered with sq, and cubic with cu, between the number and the unit (15 sq mi, 3 cu ft; not 3 ft cu). A superscript exponent indicates that the unit is squared, not the unit and the quantity (3 meters squared is 9 square meters, or 9 m²).
• In tables and infoboxes, use unit symbols and abbreviations; do not spell them out.
• Some different units share the same name. These examples show the need to be specific.
  • Use US or imperial gallon rather than just gallon.
  • Use nautical mile or statute mile rather than mile in nautical and aeronautical contexts.
  • Use long ton or short ton rather than just ton (the metric unit—the tonne—is also known as the metric ton).
• Ranges are preferably formatted with one rather than two unit signifiers (5.9–6.3 kg, not 5.9 kg – 6.3 kg).

Unnecessary vagueness

Use accurate measurements whenever possible.

Vague	Precise
The wallaby is small	The average male wallaby is 1.6 metres (63 in) from head to tail.
Prochlorococcus marinus is a tiny cyanobacterium.	The cyanobacterium Prochlorococcus marinus is 0.5 to 0.8 micrometre across.
The large herd of dugong stretched a long way down the coast.	The dugong swam down the coast in a herd 5 kilometres (3 mi) long and 300 metres (1000 ft) wide.

Currencies

See also: WikiProject Numismatics: Article titles

Which one to use

• In country-specific articles, such as Economy of Australia, use the currency of the country.
• In non-country-specific articles such as Wealth, use US dollars (US$123). Some editors also like to provide euro and/or UK pound equivalents, formatted as described in the next section.
• If there is no common English abbreviation or symbol, use the ISO 4217 standard.

Formatting

• Fully identify a currency on its first appearance (AU$52); subsequent occurrences are normally given without the country identification or currency article link (just $88), unless this would be unclear. The exception to this is in articles related entirely to the US and the UK, in which the first occurrence may also be shortened and not linked ($34 and £22, respectively), unless this would be unclear. Avoid over-identifying currencies that cannot be ambiguous; e.g. do not place EU or a similar prefix before the € sign.
• Do not place a currency symbol after the value (123$, 123£), unless the symbol is normally written thus. Likewise, do not write $US123 or $123 (US).
• Currency abbreviations that come before the number are unspaced if they consist of or end in a symbol (£123, €123), and spaced if alphabetic (R 75).
• Ranges are preferably formatted with one rather than two currency signifiers ($250–300, not $250–$300).
• Conversions of less familiar currencies may be provided in terms of more familiar currencies, such as the US dollar, euro or UK pound. Conversions should be in parentheses after the original currency, rounding to the nearest whole unit, with at least the year given as a rough point of conversion rate reference; for example, 1,000 Swiss francs (US$763 in 2005).
• For obsolete currencies, provide if possible an equivalent, formatted as a conversion, in the modern replacement currency (e.g. UK metric pounds for historical pounds-and-shillings figures), or at least a US dollar equivalent as a default in cases where there is no modern equivalent.
• When possible, always link the first occurrence of a symbol for lesser-known currencies (₮146); some editors consider it unnecessary to link the symbols of well-known currencies, but doing so can often be helpful to readers, as many countries use "dollars" or "pounds" as their base currency, and not all readers are familiar with the euro.
• The UK pound sterling is represented by the £ symbol, with one horizontal bar. The double-barred ₤ symbol is ambiguous, as it has been used for Italian lire and other currencies as well as the British one. For non-UK currencies that use pounds or a pound symbol (e.g. the Irish punt, IR£) use the symbol conventionally preferred for that currency.

Common mathematical symbols

See also: Manual of Style (mathematics).

• For a negative sign or subtraction operator, use a minus sign (−), input by clicking on it in the insert box beneath the edit window or by keying in &minus;), or an en dash (see En dashes); do not use a hyphen, unless writing code, or an em dash.
• For a multiplication sign, use ×, which is input by clicking on it in the edit toolbox under the edit window or by keying in &times; (however, the letter ex is accepted as a substitute for "by" in such terms as "4x4").
• The following signs are spaced on both sides:
  • plus, minus, plus or minus (as operators): + − ±
  • multiplication and division: × ÷
  • equals, does not equal, is approximately equal to: = ≠ ≈
  • is less than, is less than or equal to, is greater than, is greater than or equal to: < ≤ > ≥

Magnitude prefixes

Binary prefixes

Multiple-byte units
Decimal Value Metric 1000 kB kilobyte 10002 MB megabyte 10003 GB gigabyte 10004 TB terabyte 10005 PB petabyte 10006 EB exabyte 10007 ZB zettabyte 10008 YB yottabyte 10009 RB ronnabyte 100010 QB quettabyte	Binary Value IEC Memory 1024 KiB kibibyte KB kilobyte 10242 MiB mebibyte MB megabyte 10243 GiB gibibyte GB gigabyte 10244 TiB tebibyte TB terabyte 10245 PiB pebibyte — 10246 EiB exbibyte — 10247 ZiB zebibyte — 10248 YiB yobibyte — — —
Orders of magnitude of data

In computing, where binary numbers (powers of 2) are often more useful than decimal (powers of ten), the de facto standard for binary prefixes and symbols (collectively, "units") is to use kilo-, mega-, giga-, with symbols K, M, G, where each successive prefix is multiplied by 1024 (2¹⁰) rather than SI's 1000 (10³). To attempt to resolve this ambiguity, the IEC introduced in 1999 new prefixes such as kibi-, mebi-, gibi-, and symbols such as Ki, Mi, Gi, to specify binary multiples of a quantity. These replacements for the historical units have gained limited acceptance outside the standards organizations. Many publications, computer manufacturers and software companies continue to use the historical binary units (KB, MB, GB).

There is no consensus on whether to use the historical prefixes or the newer IEC standard in Wikipedia articles to represent binary units. There is consensus that editors should not change prefixes from one style to the other if there is uncertainty as to which term is appropriate within the context—one must be certain whether "100 GB" means binary not decimal units in the material at hand before equating it with "100 GiB". When this is certain, the use of parentheses for IEC binary prefixes, for example, "256 KB (KiB)" is also acceptable, as is the use of footnotes to disambiguate prefixes. Prefixes in directly quoted passages are never changed; if explanation is necessary, use a more exact measurement in square brackets.

Measures that typically use decimal multiples:

• Capacities of hard disk drives, DVDs, some floppy drives, etc.
• Computer network and bus speeds

Measures that typically use binary multiples:

• Memory and cache sizes
• CD-ROMs, some floppy drives, etc.

Orders of magnitude

See orders of magnitude and the talk page there for ongoing, possibly resolved debate on which style of exponent notation to use for large numbers.

Geographical coordinates

Geographical coordinates on Earth should be entered using a template to standardize the format and to provide a link to maps of the coordinates. As long as the templates are adhered to, the functions are performed automatically by a robot. Due to planned enhancements in functionality, this information is subject to change.

Two types of template are available:

• {{coor *}}, which is used in most articles and supported by all re-users, such as Google Earth and Wikipedia-World.
• {{coord}}, which combines the functionality of the coor family, offers users a choice of display format through user styles, emits a Geo microformat, and is supported by Google Earth.

Depending on the form of the coordinates, the following formats are available.

For just degrees, use the d mode:

{{coor d|DD|N/S|DD|E/W|}} or

{{coord|dd|N/S|dd|E/W}}

For degrees/minutes, use the dm mode:

{{coor dm|DD|MM|N/S|DD|MM|E/W|}} or

{{coord|dd|mm|N/S|dd|mm|E/W}}

For degrees/minutes/seconds, use the dms mode:

{{coor dms|DD|MM|SS|N/S|DD|MM|SS|E/W|}} or

{{coord|dd|mm|ss|N/S|dd|mm|ss|E/W}}

where:

• latitude and longitude can be signified by decimal values in degrees
• DD, MM, SS are the degrees, minutes, seconds, listed in sequence
• N/S is either N or S, depending on which hemisphere, and
• E/W is either E or W, depending on which hemisphere

For example:

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

{{coor dm|59|55|N|10|44|E|}} or

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

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

{{coor d|22|S|24|E|}} or

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

for higher levels of precision, use the dms mode:

{{coor dms|33|56|24|N|118|24|00|W|}} or

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

London Heathrow Airport, Amsterdam, Jan Mayen and Mount Baker are examples of articles that contain geographical coordinates.

• degrees can be specified with decimals, in d mode
• minutes can be specified with decimals, in dm mode
• seconds can be specified with decimals, in dms mode

Example:

{{coor d|33.94|S|118.40|W|}} or

{{coord|33.94|S|118.40|W}} or

{{coord|33.94|-118.40}}

The second and third examples become 33.94°N 118.40°W / 33.94; -118.40. The precision can be controlled by increasing or decreasing the number of decimal places. Trailing zeroes should be included.

The final field, following the E/W, is available for specification of attributes, such as type, region and scale. For more information, see the geographical coordinates WikiProject.

Templates other than {{coor *}} or {{coord}} should use the following variables for coordinates: lat_d, lat_m, lat_s, lat_NS, long_d, long_m, long_s, long_EW.

See also

• For page naming specifics, see Wikipedia:Naming conventions (numbers and dates).
• m:Help:Date formatting feature at Meta
• Wikipedia:Only make links that are relevant to the context#Dates