Writing with numbers

In many of our technical and business communications, numbers are key facts we need to express accurately and clearly. Here are some rules and some advice to remember when writing with numbers.

a. Write out a number if it begins a sentence.

Thirty-two people won an award for outstanding technical contributions.

b. Hyphenate all compound numbers from twenty-one through ninety-nine.

Forty-four people were injured in the blowout.

Twenty-three of them were hospitalized.

c. Write decimals in figures. Put a zero in front of a decimal unless the decimal itself begins with a zero.

The soil eroded back by 0.89 metres in a year.

The soil only eroded .05 metres this year because of the drought.

d. Be consistent within a category.

If you choose numerals because one of the numbers is greater than nine, use numerals for all numbers in that category. If you choose to spell out numbers because one of the numbers is a single digit, spell out all numbers in that category.

If you have numbers in different categories, use numerals for one category and spell out the other.

Correct Examples:

My 10 cats fought with their 2 cats.

My ten cats fought with their two cats.

Given the budget constraints, if all 30 history students attend the four plays, then the 7 math students will be able to attend only two plays.
(Students are represented with figures; plays are represented with words.)

Incorrect Example:

I asked for five pencils, not 50.

e. Always spell out simple fractions and hyphenate the parts (the numerator and the denominator).

One-half of the pies have been eaten.

A two-thirds majority is required for that bill to pass in Congress.

Exception: When a hyphen already appears in either part of the fraction (the numerator or the denominator), omit the hyphen between the numerator and denominator.

twenty-five thirty-seconds

three ten-thousandths

thirty-two thousandths

f. A mixed fraction can be expressed in figures unless it is the first word of a sentence.

Allow for a 1 1/2 per cent expansion rate.

One and one-half percent was the maximum expansion rate allowed.

g. The simplest way to express large numbers is best.

Round numbers are usually spelled out. Be careful to be consistent within a sentence.

You can earn from one million to five million dollars.

You can earn from one million to $5,000,000.

You can earn from five hundred to five million dollars.

You can earn from $5 hundred to $5 million.

You can earn from $500 to $5 million.

You can earn from $500 to five million dollars.

h. With numbers that have decimal points

Use a comma only when the number has five or more digits before the decimal point. When writing out numbers, use the comma where it would appear in the figure format. Use the word and where the decimal point appears in the figure format.

$15,768.13: Fifteen thousand, seven hundred sixty-eight dollars and
thirteen cents

$1054.21: One thousand fifty-four dollars and twenty-one cents

Note: If the number does not have a decimal point, still use the comma where it appears in the numerical form.

1,054 schools : one thousand, fifty-four schools

12,154 schools: twelve thousand, one hundred fifty-four schools

i. To express decades using incomplete numerals, put an apostrophe before the incomplete numeral but not between the year and the -s.

During the ’80s and ’90s, the Canadian economy grew only slightly.

During the ’80′s and ’90′s, the Canadian economy grew only slightly.

j. To express decades in complete numerals, don’t use an apostrophe between the year and the -s.

During the 1980s and 1990s, the Canadian economy grew only slightly.

k. When a written-out number or a numeral is joined to a unit of measurement and the resulting compound is used as an adjective, use a hyphen to join the number and its unit of measurement.

the 100-yard dash

a ten-day tour

a two-minute speech

a 40-hour work week

a 90-degree angle

l. Time of day in even, half, and quarter hours are usually spelled out.

The Board member expected the review to continue until half past five.

Our family always eats dinner at seven o’clock.

m. When the exact moment in time is to be emphasized, the time is usually expressed with numerals.

This Hearing is in recess until 2:00.

If we hurry we can catch the 3:20 train.

n. Avoid word-numeral doublets.

We’ve all seen this in legal documents, statements like this:

The licensee agrees to pay the licensor two hundred thousand dollars ($200,000).

Why do we do this? According to Bryan Garner in his book Legal Writing in Plain English, “comparatively few lawyers even know why they engage in the ancient habit.” Word-numeral doublets arose centuries ago as a safeguard against fraudulently altered documents; numerals are easier to alter than words. As Bryan states, “There’s no good reason why modern briefs, judicial opinions, statues, or contracts should contain doublets“.

The rule is very simple; if the numerals are clearer, only use numerals; if the words are clearer, only use words.

A Recommendation

Use a combination of figures and words for numbers when a combination will keep your writing clear.

The club celebrated the birthdays of 6 90-year-olds who were born in the city.

The reader might read ’690′ as one number.

The club celebrated the birthdays of six 90-year-olds who were born in the city.

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Last updated: January 15, 2009
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