Using Numbers for Technical Writing

While some organizations may have their own style guides outlining their unique preferences, the following 14 guidelines are how numbers should be used, absent a formal style guide in your organization.

  1. Use Arabic numbers (1, 2, 3,) for:
  • All numbers over nine in the text

There were 98,526 wafers in that batch.  There were 10 operators involved.  (But:  Ten operators were involved.)

Note that when the first word of a sentence is a number greater than nine, you have two options: (a) spell it out, or (b) re-write the sentence so it does not start with the number. The exception is a numeral that identifies a calendar year.

  • The day and year of the date:

April 10, 2014

  • Time:

5:25 A.M.;  4 P.M.

  • Address:

13535 N.W. Science Park Drive

8600 S.W. 10th Avenue

2700 N.E. Third Avenue

  • Measurements, decimals, money, percentages:

5 in.  (or 5 inches)

5.0       0.67834



  • In a series. Combine as appropriate (AP Style)

…15 cashews, three walnuts, 52 peanuts,…

  • When modifying a noun

1/8-ft. lengths,   3-1/4-in. pipe

  1. Spell out when:
  • The number is the first word in a sentence

Ten operators were involved.

  • The number is less than 10

three containers of filters

  1. Other things to remember:
  • Put a zero before the decimal point for a number less than one (0.543).
  • Line up on the decimal point for lists of numbers (e.g., in a table).
  • Combine Arabic numbers with words for large numbers (e.g, 200 million, $345 billion).
  • For contracts, checks, and other documents where a typographical error could be really serious, spell out and use Arabic numbers [nine thousand twenty four dollars and twenty cents ($9,024.20)].

Hope these number guidelines will be helpful. They will also work for general business writing. Next week: Three easy ways to “translate” your words and terms to improve non-technical reader comprehension.



Gail Tycer offers business writing workshops and presentations; executive coaching, consulting, writing, and editing services. Call Gail at 503/292-9681, or email to learn more.

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