1. General Rule
There is a significant difference between using figures and using words to express numbers. Figures are big (like capital letters) and compact and informal (like abbreviations); when used in a sentence they stand out clearly from surrounding words. By contract, numbers expressed in words are unemphatic and formal; they do not stand out in a sentence. It is this functional difference between figures and words that underlies all aspects of number style.

2. Spell out numbers from 1 to 10; use figures for numbers above 10. This rule applies to both exact and approximate numbers.

1. I would like ten copies of the report, but I need two or three copies now.
2. My boss needs 75 minutes to present his proposal.
3. We expect about 25 to 50 people to attend the meeting.
4. The advertisement is geared to the 40-plus age demographic.
5. One store has ordered 3500 copies of my book this week.
6. That web site drew more than 30,000 visitors yesterday.
7. We send out about 200,000 catalogs almost every month, but our year-end holiday catalog is mailed to over 1,000,000 households.
8. That movie drew in more than 12,000 movie fans last week.