Numbers and Units

Numbers

Decimals

For decimals less than one use a leading zero.

0.27 not .27

Figures or Words

• Generally spell out numbers below ten.
• Use figures with all abbreviated forms of units.
• Never start a sentence with a figure. To avoid spelling out large numbers recast the sentence.

Ranges

For a span of numbers use an en rule, eliding to the fewest number of figures possible.

0–1, 132–6

Do not elide numbers in the group 10 to 19.

13–16, 1213–18.

Units

Provided it is not non-dimensional a value in the text must have its associated unit.

Spacing

Use a full space between a value and the unit. Separate components of the unit with a thin space.

9.87 m s-1 (9.87\ m\,s\$^{-1}\$)

A common latex mistake is to include the unit while still in math mode.

\$9.87\ m\,s^{-1}\$ typesets the unit in italics which is wrong

Temperature

The degree symbol is printed close up to the scale abbreviation when given.

15 °C (15\ \$^{\circ}\$C).

In non-technical writing the scale is sometimes omitted in which case the degree symbol is printed close up to the number.

15° (15\$^{\circ}\$)

Values in Kelvin do not include a degree sign.

27 K (27\ K) not 27 °K

Latitude and Longitude

The degree, minute and second symbols are printed close up to the number.

36° N, 155° 13’ 10” W

Solidus

Do not use a solidus to indicate 'per'.

9.87 m s-1 (9.87\ m\,s\$^{-1}\$) not 9.87 m/s