The Blue Book of Grammar and Punctuation: An Easy-to-Use Guide with Clear Rules, Real-World Examples, and Reproducible Quizzes, 11th Edition

Chapter 4

Writing Numbers

Except for a few basic rules, spelling out numbers vs. using figures (also called numerals) is largely a matter of writers' preference. Again, consistency is the key.

Policies and philosophies vary from medium to medium. The two most influential guidebooks for publishers, editors, and writers, the Associated Press Stylebook and the Chicago Manual of Style, have different approaches. The first recommends spelling out the numbers one through nine and using figures thereafter; Chicago recommends spelling out the numbers one through ninety-nine and using figures thereafter.

This is a complex topic, with many exceptions, and there is no consistency we can rely on among blogs, books, newspapers, and magazines. This chapter will confine itself to rules that all media seem to agree on.

Rule 1. Spell out all numbers beginning a sentence.

Examples:	Twenty-three hundred sixty-one victims were hospitalized.
Nineteen fifty-six was quite a year.

Note: The Associated Press Stylebook makes an exception for years.

Example:

1956 was quite a year.

Rule 2a. Hyphenate all compound numbers from twenty-one through ninety-nine.

Examples:	Forty-three people were injured in the train wreck.
Twenty-seven of them were hospitalized.

Rule 2b. Hyphenate all written-out fractions.

Examples:	We recovered about two-thirds of the stolen cash.
One-half is slightly less than five-eighths.

Rule 3a. With figures of four or more digits, use commas. Count three spaces ...