NUMBERS

When should a number be written out rather than appear as a numeral?

A number below 10 is written out, unless it is used in an expression of time, measurement (length, volume, weight, velocity, inc.), or money:

two pages		eight attempts

31 employees		117 contracts

but

5 p.m.			8 cm

3 in.			$7 

Numbers of 10 or greater are written as numerals, which makes them easier to see and read. However, since a numeral stands out in text, nontechnical writers often write out numbers below 100 to avoid overemphasizing them.

How is the plural of a numeral written?

The plural of a numeral is formed by simply adding a lowercase "s" to it (without an apostrophe):

in the early 1900s

counted off by 2s

temperatures in the mid-70s 

If the number is written out, its plural is formed like any other word:

in bills of fives and tens

the riots of the sixties

How is a number handled when it begins a sentence?

A number appearing at the beginning of a sentence is written out:

Sixty-five years ago this was open rangeland.

Fourteen inches of insulation provided a thermal barrier.

EXCEPTION: If the number is very large, writing it out would make the number difficult to read quickly. In these situations, the sentence is rewritten:

not this

765 students responded to the request for volunteers.

nor this

Seven hundred sixty-five students responded to the

request for volunteers.

 but this

The request for volunteers elicited responses from

765 students.

How are round numbers written?

Write out round numbers (approximations):

more than six hundred entries

roughly five thousand units

over ninety failures 

Use numerals and letters for very large round numbers (1 million or greater):

nearly $90 billion

about 650 million years ago

less than 1 trillion

How are dates expressed?

Use numerals for dates:

January 20, 1960

20 January 1960

the 20th of January 1960

January 1960

How are fractions written?

Fractions appearing by themselves in text should be written out:

three-fifths of a mile

one-half inch

increased by one-fourth

However, as a fractional expression becomes longer, readability dictates that the fraction be expressed as a numeral or a decimal:

18 1/4 revolutions

67/100 (or .67)

6 13/16 in.

Numerals should also be used when expressing measurements, especially in technical documents:

5/8-inch pipe

3 1/2 centimeters

2 3/4 gallons

What if numbers smaller and larger than 10 are used in the same sentence?

Consistency is of primary concern, whether the numbers are in a sentence, paragraph, or section:

Part A has 3 pages, Part B has 29 pages, Part C has 9 pages,

and Part D has 19 pages.

Two dogs and twelve cats were placed in quarantine.

Nine units each housed 15 transformers; the remaining 5 units

each housed 12 transformers.