Business Writing Essentials
Style

Numbers

Sometimes we write numbers as words (seven), and sometimes we write numbers as digits (7). The rules about this can depend on your industry and your boss. But for most writing at work, six rules apply.

Rule 1: Spell out numbers one through ten. However, use digits to write numbers when accuracy or emphasis is desired, which is most of the time in technical writing.

So when is accuracy or emphasis not desired? Here are some examples:

[x] She has 100 things to do today.

Using digits is like adding: ", for which she has a checklist."

[+] She has a hundred things to do today.

[x] He joined the firm 5 years ago.

Using digits is like adding: "today, and here's his certificate to prove it."

[+] He joined the firm five years ago.

There are numbers for which we almost always assume accuracy is desired:

date: May 6

money: $2

time: 4 p.m.

percentage: 9 percent

ratio: 3-to-1 odds

page number: page 10

score: 7 to 5

measurement: 8 pounds

In addition to the new rule, there are time-proven guidelines:

Rule 2: Only spell out numbers that can be expressed in one or two words.

okay to spell it out:

  weighed two tons

  for six hundred dollars

  after seventy-three days

better to stick with digits:

  weighed 3,850 pounds

  for $595

  after 170 days

Rule 3: Use a combination of digits and words when it will keep things clear.

[x] We counted 40 2-pound rats.

Using all digits invites the reader to mistakenly envision rodents of unusual size.

[+] We counted forty 2-pound rats.

[+] We counted 40 two-pound rats.

Rule 4: Strive for consistency when showing similar counts.

[x] They brought two apples, 8 oranges, and 9 bananas.

[+] They brought two apples, eight oranges, and nine bananas.

[x] The vote was 12 in favor and three opposed.

[+] The vote was 12 in favor and 3 opposed.

Rule 5: Write out numbers that begin sentences (or rewrite the sentence).

[x] 20% of the measurements were in error.

[+] Twenty percent of the measurements were in error.

[+] We found that 20 percent of the measurements were in error.

[+] We found that 20% of the measurements were in error.

Rule 6: Add a lower case s (without an apostrophe) to form the plural of a number in digits.

[x] He was in his 20's during the 1990's.

[+] He was in his 20s during the 1990s.

Lesson: Numbers
Module: Style
Course: Business Writing Essentials