Deviates from CMoS
See also Dates, Decades & Centuries; Weights & Measures
In general, spell out numbers from one to nine, but use numerals for all units of measurement (except time) and with mixed fractions.
six to 11 buses a day; 2½ times the original price; 3km; two minutes
Do not start sentences with numerals.
Twenty-seven people attended the performance.
Don’t use numerals with very general approximations.
Several hundred people attended.
But:
About 5km down the road
Use decimals for all distances.
It is 33.5km away.
Use fractions for time, as decimals can be confused with minutes or seconds.
It takes 1½ hours to get there.
If ‘half’ is used on its own, write it out.
Only half the population can read.
Follow house style for numbers in headings, eg Top Five Museums, Top 10 Restaurants, unless otherwise directed in the relevant style sheet or product manual.
See also CMoS 9.8
Do not use a comma until 10,000; spell out ‘million’ and ‘billion’ (also applies to maps).
9999; 10,000; 12 million; seven billion
Note: in LP text ‘billion’ is 109 (a thousand million).
When high numbers appear with a unit of measure, numerals are used.
$5 million; 7 billion tonnes; 2 million sq km
When high numbers are used with a currency or measure that sits after the numeral (eg vatu), spell out the million/billion as normal, and retain the currency/measure at the end of the figure.
6.5 million vatu
12.5 million sq km
Use numerals with fares, floors, centuries, classes of bus/train, and editions of books and other publications, even when the number is less than 10.
1st-class fare; 6th floor; 3rd century
Elsewhere, write out first, second etc. The usual rule for numbers greater than nine applies.
the first president of the United States; the 11th earthquake this decade
Use the local convention for street names (eg Fifth Ave in New York, 3rd Ave in San Francisco).
Use a hyphen to represent negative numbers.
-10°F
Repeat only numbers that have changed, with the exception of numbers in the teens.
20–1
252–65
14–15
318-19
Use numerals with room numbers.
The view from room 6 is sensational.
Spell out round numbers (hundreds, thousands, hundred thousands and millions).
There were tens of thousands of people at the demonstration.
Repeat entire number to avoid confusion.
172–176 Argyll Dr
Use numerals with vehicle, platform and ticket-window numbers.
train 2
platform 5