Bite Size Grammar Tip: How to Write Numbers in Essays

It is important for writers to recognize and to understand how to express numbers in formal writing, and to be able to determine when to write out numbers into words and when to use figures or numerical digits. Although the leading guides, The Chicago Manual of Style and The Associated Press Stylebook, offer differing approaches when it comes to American English grammar rules, as long as writers are consistent within their own writing, the expression of numbers in formal writing can be varied. Keep in mind that with each varying discipline, the number expression can also follow different rules.   Below are helpful rules for most writers to follow when engaged in formal writing.

Numbers Smaller Than Ten

• Spell out smaller numbers such as whole numbers that are smaller than ten. Especially in formal writing, it is important to spell out the numbers, otherwise it looks too informal.

One-Word Numbers vs. Two-Word Numbers

• Although there is no consensus on the application of this rule, here is a good rule of thumb to follow. For any one-word number, such as thirteen or thirty, it should be spelled or written out. For any two-word number, such as 36 or 42, the number should be expressed in figures.

Hyphenated Numbers and Fractions

• For compound or two-word numbers, use a hyphen for numbers twenty-one through ninety-nine. For example, “thirty-four students attended the club meeting” rather than “34 students attended the club meeting.”
• Hyphenate all fractions that are spelled out. For example, “My sister ate three-fourths of the pie.”

Time Periods

• When referencing time such as decades or centuries, these figures should be spelled out and they should not be capitalized. Use seventeenth century and the seventies, rather than 17^th and 70s, respectively.

Never Start a Sentence With a Numerical Figure

• If a writer begins a sentence with a number, then the number must be spelled out. For example, “Fourscore and seven years ago” should not be written as “4 score and 7 years ago.” If a sentence includes a larger number within the sentence, it can be written as digits. For example, “There were 50,000 fans who attended the concert.”

Recipes and Percentages

• For informal and daily writing, writers can use numerical digits to refer to percentages such as “15% of the students” and recipes such as “Add 3 cups of sugar.” For formal writing, percentages should be spelled out, such as “15 percent of teachers.”

Neighboring Numbers

• If the writing includes two numbers that are next to one another, spell out the number that has the least amount of letters when spelled out. It is confusing to readers if there are too many numbers written next to each other; therefore, write one of the numbers as a digit and the other spelled out. For example, write “four 18-year-olds” rather than “4 18-year-olds.”

Ordinal numbers

• An ordinal number is a number that defines an object or a thing’s position in a series such as “first,” “second,” or “third.” When using ordinal numbers, spell out the number. Write “The baseball player made it to second base” rather than “The baseball player made it to 2^nd base.”

Time

• When using time markers such as midnight or noon, do not write out the number such as 12:00AM and 12:00PM.
• When writing about a time of day, write the numerical digits, such as 5:30p.m. or 1:30 sharp.
• AM and PM can also be written as A.M and P.M or a.m. and p.m. Some writers choose to place a space between the time and AM or PM (7 AM, 4:15 P.M., 3:30 p.m.) while others choose not to leave a space (7AM, 4:15P.M., 3:30p.m.).

When composing a formal piece of writing, consider now how you might express the use of numbers.