In the body of an article, generally spell out single-digit whole numbers from zero to nine; write those greater than nine as numerals, but spelling them out is acceptable if they are expressed in one or two words (16 or sixteen, 84 or eighty-four, 200 or two hundred, but 3.75, 544, 21 million). This also applies to ordinal numbers (16th or sixteenth). Exceptions:
- Limited space. Use numerals in tables, infoboxes, and other places where space is limited, but numbers in a table's explanatory text and comments should be consistent with the rules above.
- Comparable quantities. 5 cats and 32 dogs or five cats and thirty‑two dogs, not five cats and 32 dogs.
- Adjacent quantities that are not comparable. thirty-six 6.4-inch rifles, not 36 6.4-inch rifles.
- Sentence openings. Spell out the number or recast the sentence.
- Centuries. the 5th century CE; 12th-century manuscript.
- Simple fractions. Normally spell them out; use the fraction form if they occur in a percentage or with an abbreviated unit (⅛ mm or an eighth of a millimeter), or if they are mixed with whole numbers. Decimal fractions are never spelled out.
- Mathematical quantities, measurements, stock prices. Normally state them in numerals.
- Proper names, idioms, formal numerical designations. Comply with common usage (Chanel No. 5, 4 Main Street, 1-Naphthylamine, Fourth Amendment, Seventeenth Judicial District, Seven Years' War).
- Decimal separators. Use commas to break the sequence every three places: 2,900,000.
- Default approximation. Large rounded numbers are generally assumed to be approximations: the population is 2 million, not the population is approximately 2 million; qualify only where the approximation could be misleading. By contrast, 2,000,000 is assumed to be exact.
- Over-precise values. Avoid 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 often 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. Preferred in scientific contexts (6.02 × 1023).
- Abbreviation for million. Where values in the millions occur a number of times through an article, upper-case M may be used, unspaced, but spell it out on first occurrence.
- Billion. A thousand million (109). After the first occurrence in an article, it can be abbreviated to unspaced bn ($35bn).* *
- Not a comma. 6.57, not 6,57.
- Consistency. Make the number of decimal places consistent within a list or context (41.0 and 47.4 percent, not 41 and 47.4 percent), unless the items were measured with unequal precision (unusual).
- Leading zero. (0.02, not .02); exceptions are performance averages in sports where a leading zero isn't commonly used, and common usage such as .22-caliber.
- Word or symbol. Percent or per cent are commonly used to indicate percentages in running prose; % is more common in scientific or technical articles, and in listings, and should be used in tables and infoboxes.
- Spacing. 71%, not 71 %.
- Repetition. Normally 22–28%, not 22%–28%.
- Change of rates. Use 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%). A basis point is a hundredth of a percentage point.
- Conversions. When different parts of the English-speaking world use different units for the same measurement, use a "primary" unit in the text followed by a conversion in parentheses: the Mississippi River is Template:Convert long; the Murray River is Template:Convert long. Use the following rules to decide what the primary unit is:
- Default primary units: SI. Generally use SI and associated units (sometimes loosely called "metric units"). However, in topics strongly associated with places, times or people, make the units most appropriate to them primary. In particular:
- Consistency. Choose primary and converted units consistently in an article unless there is a good reason to diverge from this. (For example, UK-related articles in which SI units are primary may use imperial primary units for items where metric units have not yet been adopted in the UK.)
- Exceptions to the need to convert:
- Scientific articles. Conversions to customary or imperial units may be dispensed with if there is consensus to do so; in these cases, spell out or link the first occurrence of each unit.
- Idiom. In some cases, inserting a conversion would be awkward (the four-minute mile).
- Symbols or words? In the main text, give the primary units as words and use unit symbols or abbreviations for conversions: 100 millimetres (4 in) or 4 inches (100 mm). However, where there is consensus, abbreviate the main units too, but name them fully on their first occurrence.
- Levels of precision. Converted values should use a level of precision similar to that of the source value, so the Moon is 380,000 kilometres (240,000 mi) from Earth, not (236,121 mi). Convert small numbers to a higher level of precision where rounding would cause a significant distortion, so one mile (1.6 km), not one mile (2 km).
- Be precise if possible. Not Wallabies are small, but The average male wallaby is 1.6 metres (63 in) from head to tail.; not Prochlorococcus marinus is a tiny cyanobacterium., but The cyanobacterium Prochlorococcus marinus is 0.5–0.8 micrometres across.*
- Direct quotations. Put Wikipedia's conversions for units within square brackets.
- Clarify ambiguous units.* In a few cases, different units share the same name. Specify:
- Spelling. American English uses -er endings for metric units: liter, kilometer; all other varieties, including Canadian, use -re: litre, kilometre.
- Conversion templates. These templates—including start-convert-end, which inserts a non-breaking space—can be used to convert and format many common units.
- No dots. Standard abbreviations and symbols for units are undotted (m, not m. for metre/meter; ft, not ft. or ′ for foot).
- Plurals. Don't append an s for the plurals of unit symbols: kg, not kgs.
- Hard spaces. Always insert (
) between numeric values and unit symbols (25 kg, not 25kg). Exceptions: the symbols for percent (25%) and for degrees, minutes and seconds of plane angle (5° 24′ 21.12″ N, and a 90° angle).
- Hyphens. When values and spelled-out units form a compound adjective, hyphenate them: 10-kilometer beach, but 10 km beach.
- Ranges. Preferably 5.9–6.3 kg, not 5.9 kg – 6.3 kg).* *
- Temperatures. Always accompanied by °C for degrees Celsius, °F for degrees Fahrenheit, or K (never °K) for kelvin. Insert a hard-space (
) between value and temperature symbol: 35 °C, 62 °F, and 5,000 K.
- Degree symbol. ° (°), not º or ˚.*
- Squared and cubic units. Metric: use a superscript exponent (5 km2, 2 cm3). Imperial and US: 15 sq mi, 3 cu ft. Use
<sup>3</sup>to produce the superscripts 2 and 3; don't use the Unicode ² and ³.
- Limited space. In tables and infoboxes, use symbols and abbreviations, not words.
- Familiar versus technical. Use generally familiar units unless the article is highly technical and the sources use specialized units. For specialized situations, see MOSNUM
- Country-specific articles. Use the currency of the country; e.g., Economy of Australia.
- Non-country-specific articles. Use US dollars; e.g., Economics.
- Full or short form? Use the full name on its first appearance (52 Australian dollars), and thereafter the symbol (just $88), or the full abbreviation (AU$) if necessary to distinguish from other currencies that use the same symbol. The exception to this is in articles related entirely to US-, UK- or Eurozone-related topics, in which the first occurrence may be shortened ($34, £22 and €26) if clear.
- Shortage of space. Use the short forms in tables, infoboxes and parenthetical notes.
- Order of elements Don't invert (123$, 123£, 123€), unless a symbol is normally written as such. Don't write $US123 or $123 (US).
- Spacing. Currency abbreviations that come before the number are unspaced if they consist of or end in a symbol (£123), and spaced if alphabetic (R 75).
- Default to ISO. If there is no common English abbreviation or symbol, use the ISO 4217 standard.
- Ranges. Preferably format with one rather than two currency signifiers ($250–300, not $250–$300).
- Conversions. Less familiar currencies may be converted to more familiar currencies in parentheses after the original currency, rounding to avoid false precision and noting the conversion as approximate, with at least the year given; e.g., Since 2001 the grant has been 10,000,000 Swedish kronor (about US$1.4M Template:As of).
- Obsolete currencies. If possible, provide a conversion in the modern replacement currency (e.g., decimal pounds for historical pre-decimal pounds-and-shillings figures), or at least a US-dollar equivalent where there is no modern equivalent.
- Linking. If possible, link the first occurrence of lesser-known currencies (146 Mongolian tögrögs).
- Lower case. Don't force capital letters on the names of currencies, currency subdivisions, coins and banknotes.
- Pound sterling. The symbol is £, with one horizontal bar. For non-British currencies that use a pound symbol, use the conventional symbol for that currency.
- Minus sign. For a negative sign or subtraction operator, use a minus sign (−) by clicking on the edit tool under the edit window or by typing
−(don't use a hyphen (-) unless writing code).
- Multiplication sign. Between numbers, use ×, input by clicking on it in the edit toolbox under the edit window, or by typing
×. Don't use an w:asterisk (*) unless writing code). Don't use the letter "ex" (x, although this is acceptable as a substitute for by in such terms as 4x4.
- Spacing. Symbols for w:binary operators and relations are spaced on both sides: + − ± × ÷ = ≠ ≈ < ≤ > ≥
- Exponential notation. an (typed as
a<sup>n</sup>), not a^n. Don't use E notation.
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