Numerals

AP Stylebook: Numerals

In general, spell out one through nine. Use figures for 10 or above and whenever preceding a unit of measure or referring to ages of people, animals, events, or things.

Decimals

AP Stylebook: Decimals

If a unit of measure follows the numeral, use the decimal format, not fractions.

1.75 mg (NOT 1 3⁄4 mg)

2.5 kg (NOT 2 1⁄2 kg)

If the value is less than 1, insert a zero before the decimal point.

0.2 g (NOT .2 g)

0.9 mg/kg

Fractions

AP Stylebook: Fractions

Ordinals

Ordinals generally express ranking rather than quantity, so spell out first through ninth, and use the numeral for 10th and above. Do not use superscript for ordinals.

Examples:

The fourth patient was admitted in critical condition.
The 12th patient died shortly after his arrival.

When you have a mixture of ordinals below and above nine, use numerals. This is a divergence from AP Style. 

Example: The 5th and the 12th patients showed similar symptoms.

Percent, percentage, percentage points, %

AP Stylebook: Percentages

Singular and plural

When the quantity is less than 1, the unit of measure is singular.

Examples:

0.5 gram (NOT grams)

0.2 second (NOT seconds)

Spacing

Insert a space between the numeral and the symbol, except for %, °C, °F, ° (for angles),
money symbols, fractions, and inches/feet symbols.

25 g
30%
£250

40 mL
28.5°C
CHF 50*

60 kg
4"
5 ½ years

*a space is added because CHF is the abbreviation for the Swiss Franc currency and not a symbol.

Units of measure

Abbreviated units of measure do not have a period, unless they close a sentence.

Examples:

50 mg (NOT 50 mg.)

2 dL (NOT 2 dL.)

This page last reviewed on November 14, 2023