The methods of how to write numbers varies widely, according to the style one chooses to follow. Style is a set of preferences in language and punctuation usage, it standardizes the output of a particular publisher or industry. There are many style guides. In order to know which style guide it is appropriate to use, consider your audience. We will look at some common conventions for writing numbers, and some variances according to the style one is following.
- Numbers under ten should be written as words. Almost all style guides stipulate that the numbers zero through nine should be written out. However, if the number is a dimension, measurement, hours, minutes or seconds, age, or percentage, it should usually be written as a numeral.
- Compound numbers should be hyphenated. Examples: twenty-nine, thirty-three, sixty-six. Style guides vary on whether numbers over the amount of nine should be written as words or as numerals. If the number is a dimension, measurement, hours, minutes or seconds, age, or percentage, it should be written as a numeral.
- Fractions under the amount of one should be hyphenated. Examples: three-quarters, two-fifths, one-third. Usually, a mixed fraction is expressed as a numeral. Examples: 1 3/4, 2 1/2.
- Numbers over one hundred should not contain the word “and”. Examples: one hundred one, one hundred eleven, one hundred twenty-one.
- Two related numbers in a sentence should match in style. For instance, if one is writing about a choice between nine cookies or twenty-five cookies, the numbers should match in style. Example: “The box contained either 9 cookies or 25 cookies.” Normally the number 9 would be spelled out, but it is easier to read the sentence when both numbers are written as numerals.
- When a number is the first word in a sentence, it should be written out. Example: “Thirty-six ducks swam across the lake.”
- When two numbers are next to each other, write out one and use numerals for the other. Examples: twelve 4-year olds, twenty-five 2-by-fours, three 1-mile hikes.
- Figures in the millions and billions are usually written with a numeral and a word. Examples: 3 billion, 2.8 million, 16 million. The exception would be a situation in which the exact figure is important.
While the correct spelling of written numbers is constant, whether one should use the written spelling of a number or a numeral can vary according to one’s audience and the style guide one chooses to follow. When in doubt, stick with the choices that make your work easy to read, and be consistent.