V. NUMBERS

1) For numbers under 10, use number words (one, two, etc.).

2) Use numerals for all numbers 10 or over, including ordinals, e.g., 22nd.

3) Days of the month should be written in numeric form, omitting rd, th, st, nd.

April 6, June 1

4) Use numerals (and standard marks, as below) for degrees, ratios, percentages, persons’ ages, and course or program credit hours.

longitude 67°03'06"W
21.5°F below zero
6 percent
7 years old
3 credit hours

5) In order to maintain consistency within a series, use numerals if more than half of the numbers are 10 or over; otherwise use number words within a series.

22 hours, 12 minutes, 6 seconds

Twelve hats, five purses, five umbrellas, seven sweaters, and sixteen pairs of shoes were sold yesterday.

6) When numbers are cumbersome to use, use numerals instead, but use the words million, billion, etc.

5-3/4
17.9 million
3 million (note use of decimal point, since 3,000,000 is being represented)

7) Use hyphens when writing phone numbers, e.g., 800-555-1212 or 401-792-2075. When set in display, precede the number by Phone: or Fax:. Do not allow phone numbers to be broken at the end of a line and continued on the next.

8) When listing grade point averages, carry the average out to the hundredths, e.g., 3.00, not 3.0.

9) Use extended zip codes wherever possible.

10) A hyphen is not used to join numerals and the words million, billion, etc., even in a phrase like the athletic department’s $200 million capital campaign.

11) Avoid unnecessary zeroes.

a) Hours of the day should be expressed like 7 p.m. or 7:30 p.m. Do not use 7:00 p.m. except in lists of events, etc., to preserve alignment of type, or for formal invitations.

b) Keep amounts of money simple as well, with the dollar sign--unless tabulated in columns.

$3, not $3.00

12) Do not begin a sentence with a numeral; use the number word (twenty-seven, three hundred, etc.), or precede the reference to a number with other text (rearrange the sentence). Please note that number words under 100 (and those parts of numbers words for numbers above 100) should be hyphenated when they consist of two words.

Thirteen is my lucky number.
When it comes to lucky numbers, mine is 13.
Thirty-nine

13) Do not add a numeral in parentheses after use of a number word.

three copies, not three (3) copies

14) Use hyphens to set off fractions if fractions are not available in a particular font: 8-1/2" x 11".

Note: When in doubt, refer to the Chicago Manual of Style for specific usages.