10 Numbers

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Numbers from one to ten inclusive are written in text as words, whereas numbers from 11 upward are written as numerals, with the following exceptions:

Always use arabic numerals for dates, percentages, money, measurements, ages, ratios and scales.
Write out any number that begins a sentence, e.g. <correct-text-bold>Fifteen<correct-text-bold><correct-text> people were present<correct-text>.
Use numerals where a number accompanies a unit, e.g. <correct-text-bold>5<correct-text-bold><correct-text> cm<correct-text>, <correct-text-bold>7<correct-text-bold><correct-text> percent<correct-text>, <correct-text>USD <correct-text><correct-text-bold>2<correct-text-bold>.
When providing two or more numbers that refer to the same subject and at least one of them is over ten, use arabic numerals, e.g. <correct-text>The number of replies varied, ranging between <correct-text><correct-text-bold>2<correct-text-bold><correct-text> and <correct-text><correct-text-bold>12<correct-text-bold><correct-text> per group<correct-text>.
For units of time, applying the rule can be at the discretion of the writer, as long as it is consistent throughout the document (<correct-text-bold>5<correct-text-bold><correct-text> days<correct-text> or <correct-text-bold>five<correct-text-bold><correct-text> days<correct-text>).

For decimals:

Use a point (a full stop, not a comma), e.g. <correct-text>14<correct-text><correct-text-bold>.<correct-text-bold><correct-text>36<correct-text>.
Use a zero before the decimal point for numbers smaller than 1, e.g. <correct-text-bold>0<correct-text-bold><correct-text>.23<correct-text>.
Use the plural for any decimal number above 1.0, e.g. <correct-text-bold>1.5<correct-text-bold><correct-text> days<correct-text>.

For large values:

Use spaces, not full stops or commas, to denote thousands (e.g. <correct-text>10 000<correct-text>;<correct-text> 125 500<correct-text>). Use non-breaking spaces to avoid number divisions at the end of lines. It is acceptable to write <correct-text>1000<correct-text> through <correct-text>9999<correct-text> with no space where a space would look awkward (particularly in titles or headings) and when it is not specifically compared with another number in the thousands or higher, where the space would be required, e.g. <correct-text>between <correct-text><correct-text-bold>5 000<correct-text-bold><correct-text> and <correct-text><correct-text-bold>10 000<correct-text-bold>.
Do not use spaces for years (e.g. <correct-text>2007<correct-text>) or page numbers (e.g. <correct-text>p. 1402<correct-text>).
For millions, use numerals separated by non-breaking spaces (e.g. <correct-text>150 324 399<correct-text>) unless the last six numerals are zeros, in which case express these digits as <correct-text>million<correct-text> (e.g. <incorrect-text>150 000 000<incorrect-text> should be written as <correct-text>150 <correct-text><correct-text-bold>million<correct-text-bold>). The same principle holds for billions, trillions, etc. Data are in general reported to three significant figures.
FAO uses the short scale for billions and trillions: <correct-text>1 billion<correct-text> = one thousand million or 1 000 000 000 (10⁹); <correct-text>1 trillion<correct-text> = one million million or 1 000 000 000 000 (10¹²).

Write fractions in words rather than numbers, using a hyphen, e.g. <correct-text>one-third<correct-text>.

Avoid the use of roman numerals except in established terminology, e.g. <correct-text-bold>Type II<correct-text-bold><correct-text> error<correct-text>.

Where possible, write out ordinal numbers in full, e.g. <correct-text>the <correct-text><correct-text-bold>Thirteenth<correct-text-bold><correct-text> Session of the FAO Committee on Fisheries<correct-text>. Where it is necessary to use numerals, do not use superscript for the ordinal indicator, e.g. <correct-text>the <correct-text><correct-text-bold>13th<correct-text-bold><correct-text> Session<correct-text>, not <incorrect-text>the 13<incorrect-text>^th<incorrect-text> Session<incorrect-text>.

Avoid the use of adverbial ordinal numbers (<incorrect-text>firstly<incorrect-text>, <incorrect-text>secondly<incorrect-text>, <incorrect-text>thirdly<incorrect-text>, etc.), as subsequent numbers sound awkward. Replace these with <correct-text>first<correct-text>, <correct-text>second<correct-text>, <correct-text>third<correct-text>, etc.

For telephone numbers, be consistent in the use of parentheses and spaces. Always include the country code using this format: <correct-text>(+39)<correct-text> or <correct-text>(+505)<correct-text>. The recommended style is: <correct-text>(+39) 06 57057051<correct-text>.

To refer to a specific page: <correct-text>p. 40<correct-text>. To refer to a page range: <correct-text>pp. 40–42<correct-text>. To refer to the total number of pages in a publication: <correct-text>120 pp.<correct-text>

10.1 Units

Use the International System of Units (metric system) with equivalents in parentheses if necessary.

In general, use <correct-text>tonnes<correct-text> (equal to 1000 kg), not <incorrect-text>tons<incorrect-text> (2240 lb or approximately 1016 kg). A <correct-text>tonne<correct-text> is sometimes referred to in the United States as a <incorrect-text>metric ton<incorrect-text>, but always use the word <correct-text>tonne<correct-text>. A <correct-text>megatonne (Mt)<correct-text> is equivalent to <correct-text>one million tonnes<correct-text>.

For shipping, <correct-text>tons<correct-text> may however be appropriate. A <correct-text>shipping ton<correct-text> is used to measure the volume of freight, equivalent to 40 cubic feet (1.1 m³) in the United States, or 42 cubic feet (1.2 m³) in the United Kingdom.

Always give temperature in Celsius, not Fahrenheit, e.g. <correct-text>35.5 °C<correct-text>.

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TABLE 10.1 Common units

Unit

Symbol

metre

square metre

m²

cubic metre

m³

micron

litre

l, L

gram

tonne

second

degree Celsius

°C

degree absolute

kilocalorie

kcal

Source: Adapted from Bureau International des Poids et Mesures. 2019. The International System of Units (SI). [Cited 1 October 2021]. https://www.bipm.org/documents/20126/41483022/SI-Brochure-9-EN.pdf/2d2b50bf-f2b4-9661-f402-5f9d66e4b507

Do not use punctuation or letter spacing in such units as cm, mm, g, °C. Note, however, that there should always be a non-breaking space between the number and the unit, e.g. 3 cm, 70 g, 37 °C.

Do not use the plural for abbreviations of units (e.g. 7 kg, not 7 kgs). To indicate per, use /, as in 3 m/s (rather than 3 m s^-1).

Avoid combinations of three units such as: <incorrect-text>Production is 25 tonnes/ha/year<incorrect-text>. Prefer: <correct-text-bold>Annual<correct-text-bold><correct-text> production is <correct-text><correct-text-bold>25 tonnes/ha<correct-text-bold>. Exceptions may be made for statistical documents.

In series of measurements, use the symbol each time: <correct-text>10 <correct-text><correct-text-bold>cm<correct-text-bold><correct-text>, 20 <correct-text><correct-text-bold>cm<correct-text-bold><correct-text> and 50 <correct-text><correct-text-bold>cm<correct-text-bold>, not <incorrect-text>10, 20 and 50 cm<incorrect-text>.

Correct ways of writing latitude and longitude include: <correct-text>10°30' north<correct-text>; <correct-text>90° west<correct-text>; <correct-text>the zone from 10° to 40° north<correct-text>. Use the abbreviations <correct-text>N<correct-text>, <correct-text>E<correct-text>, <correct-text>S<correct-text> and <correct-text>W<correct-text> only in tables. For minutes and seconds of latitude or longitude (<correct-text>41°16'40" south<correct-text>) a straight apostrophe or straight quotation mark may be used rather than the prime symbol (<incorrect-text>‘<incorrect-text>).

If your reader may not immediately understand the unit abbreviation, include it in the list of abbreviations or spell out the full name once: <correct-text>100 hectares (ha)<correct-text>.

10.2 Percentages

Use <correct-text>percent<correct-text> (never <incorrect-text>per cent<incorrect-text>) rather than the symbol <incorrect-text>%<incorrect-text> in text, e.g. <correct-text>Exports increased by 16 <correct-text><correct-text-bold>percent<correct-text-bold><correct-text> in the last quarter<correct-text>. In tables and figures, use the symbol with no space between the number and the symbol, e.g. <correct-text>16%<correct-text>.

10.3 Dates

Write dates in this order: <correct-text>Monday, 16 October 2000 <correct-text>(with no comma between the date and the month, or the month and the year). Do not use ordinal numbers for dates (e.g. <correct-text>1 January<correct-text>, not <incorrect-text>1st January<incorrect-text>).

Avoid starting a sentence with a year, but if it is unavoidable it must be written out: <correct-text-bold>Nineteen ninety-eight<correct-text-bold><correct-text> was not a leap year.<correct-text> Do not abbreviate years, e.g. <correct-text>1985<correct-text>, not <incorrect-text>’85<incorrect-text>. Decades are referred to in complete numerals (e.g. <correct-text>the 1990s<correct-text>; not <incorrect-text>the nineties<incorrect-text>, <incorrect-text>the ’90s<incorrect-text> or <incorrect-text>the 90s<incorrect-text>).

When indicating a range of values or dates, there are two possible forms:

<correct-text>from ... to<correct-text> or <correct-text>between ... and<correct-text>, e.g. <correct-text>from 1970 to 1987<correct-text>; or
with an en-dash, e.g. <correct-text>The 1970–1987 period was ...<correct-text>

Do not combine the two forms, e.g. <incorrect-text>from 1970–1987<incorrect-text>.

A standard range of dates (<correct-text>2015–2025<correct-text>; <correct-text>from 2015 to 2025<correct-text>) implies the whole period from the beginning of 2015 to the end of 2025 inclusive. Note that for a crop or fiscal year, exceptionally, an abbreviated version should be used (<correct-text>2015/16<correct-text>, not <incorrect-text>2015/2016<incorrect-text>). When used in tables, multiyear ranges or averages may take a hyphen to denote the three-year period and an en-dash between the two sets, e.g. <correct-text>1997-99–2015-17<correct-text>.

Centuries should be written out in full, e.g. <correct-text>the twenty-first century<correct-text>, not <incorrect-text>the 21st century<incorrect-text>.

Where necessary to avoid confusion, use <correct-text>BCE<correct-text> (before Common Era) or <correct-text>CE<correct-text> (Common Era) for dates, placing the abbreviation after the year (e.g. <correct-text>1000 <correct-text><correct-text-bold>BCE<correct-text-bold>).

10.4 Time

The use of the 24-hour system is preferred, e.g. <correct-text>08.00<correct-text>, <correct-text>13.30<correct-text>. Where it is necessary to use the 12-hour system, use full stops as follows: <correct-text>8 a.m.<correct-text>, <correct-text>1.30 p.m. <correct-text>Be consistent.

Use a non-breaking space between the number and the unit.

When referring to time zones, prefer Universal Time Coordinated, i.e. <correct-text>UTC +<correct-text> or <correct-text>–<correct-text>. For example, <correct-text>The meeting will be held at 17.00 (<correct-text><correct-text-bold>UTC +6<correct-text-bold><correct-text>)<correct-text>.

10.5 Currencies

Rather than the currency symbol (which sometimes fails to convert across different software programs), use the ISO currency code given in NOCS, with a non-breaking space between the code and the amount, e.g. <correct-text-bold>USD<correct-text-bold><correct-text> 700 000<correct-text> rather than <incorrect-text>US$700,000 <incorrect-text>and <correct-text-bold>EUR<correct-text-bold><correct-text> 800 000<correct-text> rather than <incorrect-text>€800,000<incorrect-text>. For amounts of less than one unit of currency, use a zero followed by a decimal point (i.e. <correct-text>USD 0.20<correct-text> rather than <incorrect-text>20 cents<incorrect-text>).

To facilitate comparison of amounts in different currencies within a text, try to give an indicative equivalent in USD, or provide an exchange rate (either in a footnote or following the list of abbreviations). The exchange rate provided or the one used to calculate the indicative equivalent should be that valid at the date referenced, rather than at the time of writing or editing.

10.6 Mathematics and equations

Relational and operational signs have a space on either side of them (e.g. <correct-text>3 + 2 = 5<correct-text>). Use the multiplication sign <correct-text>×<correct-text>, not lower case letter <incorrect-text>x<incorrect-text>. Use the minus symbol <correct-text>−<correct-text>, not the hyphen <incorrect-text>-<incorrect-text> or en-dash <incorrect-text>−<incorrect-text>. Use the minus symbol when indicating a negative number. See Appendix 3 Useful shortcuts and functions in Microsoft Word.

Symbols used for variables, including Greek characters, should be italicized.

In chemical formulae, use subscript (indicating molecules), e.g. CO₂. Only use CO2 where it is impossible to use subscript. Superscript indicates atomic charge, as in Ba²⁺.

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