Conventions of Composition Rule 123

Rule: Represent numbers in words, not figures, as a general rule, in formal writing. You may use figures for dates (as in April 4, 2002 [omit st, nd, rd, th]); any number requiring more than two words (as in 123); numbers in a set of statistics; page, line, chapter, act, or scene, etc.; or street-numbers. If a number is the first word in a sentence, you must write it out, even if it meets one of the above criteria for writing it as a number.

Note: Multi-word numbers from twenty-one to ninety-nine are hyphenated if used as adjectives. Higher numbers: one hundred and twenty-one, etc.

Examples:

Correct: Nineteen hundred fifty four marked a watershed year for the United States.

Correct: In 1954, our Supreme Court decided one of its most important cases ever.

Correct: I had twenty-seven dresses, but not a thing to wear to the wedding.

Practice deciding which numbers to spell out:

1. I bought 10 pies, 6 doughnuts, and 200 gummy worms during the time I lived at 11 Interlaken Road.
2. Jackie's 137 home runs and Michael's 2186 dunks make them stand out forever as greats.
3. Between 10 and 15 kids each year go on semester programs.
4. 100 percent of the kids on that team plan to play in the WNBA.

Resources for further explanation of when to spell out numbers:

Grammarly's When Should I Spell Out Numbers?

Purdue OWL's Writing Numbers