Let the following rules be your guide to the use of numbers in your writing. Spell out numbers, instead of using figures to express them, in the following instances:
- Spell out a number that is less than 10 within a sentence.
- Spell out numerals that appear at the beginning of a sentence or heading
(e.g., Four years ago, he sold his house and moved away.).
- Spell out related numbers that appear at the beginning of a sentence, separated by no more than three words from, are treated alike (e.g., Ten or twelve miles farther, the rain changed to snow.).
- Spell out numbers that form part of proper names (e.g., Six Mile Creek) or mentioned in connection with serious and dignified matter, such as legal proclamations, or in formal writing.
- Numbers larger than 1,000, if spelled, should be in the following form:
Five thousand and thirty
Two thousand six hundred and eighteen
- Spell out numbers of less than 100 that precede a compound multiplier. (e.g., four 6-gun turrets).
- Spell out indefinite expressions (e.g., during the sixties, ten or twelve reasons, between three hundred and four hundred guests).
However, the use of such words as almost, about, approximately, etc., do not constitute indefinite expressions (e.g., about 60 years old, about 6 pounds in weight). Similarly, 2 to 5 million, mid-1960s, 20-odd people, and 5-fold are correct.
- For typographic appearance and easy understanding, spell out million and billion in large numbers that begin with million or billion (e.g., $7 million, $45 billion).
- Use figures, instead of spelling numbers, in testimony, hearings, transcripts, and Q and A matters, for years, sums of money, decimals, street numbers, and for numerical expressions beginning with 101.