Sooner or later you’ll need to express numbers in your writing. So, should they be written out in words or as figures?
Does it surprise you that the answer is: “It depends…”?
Good luck finding standard rules for expressing numbers and numerals across all types of writing. To complicate matters further, the rules change depending on what part of the planet you call home.
Numerical diversity notwithstanding, there are some rules applicable to general writing that most copy editors in the United States agree should be followed.
Here are seven of the most common rules.
1. Spell out whole numbers smaller than 10.
The Associated Press, New York Times, and APA style guides agree on this point. However, the Chicago and MLA style guides disagree. (I won’t complicate things by pointing out all the differences; suffice it to say that spelling out one through nine is the most common style.)
2. Don’t begin a sentence with a numeral.
The easiest way to stay congruent with this rule is to rewrite a sentence. Consider changing “Four hundred twenty-five people will participate in the medical study” to “The medical study has 425 participants.”
3. Use commas as a thousands separator.
This makes large numbers easier to read—both in print and on screen. “The stadium has 37,000 seats.”
4. Spell out estimated or rounded large numbers.
“About 1 billion people used TikTok in 2021” is easier to read than “About 1,000,000,000 people used TikTok in 2021.”
5. Spell ordinal numbers smaller than “10th” if you are indicating a sequence in time or location.
“It wasn’t until the 11th hour that we finally had our third bid on the house.”
6. Use figures for weight and dimensions, and spell out the unit of measurement. Include hyphens when the measurement becomes a compound modifier.
“She is 5 feet tall.” “The dog weighs 3 pounds, 3 ounces.” “The 5-foot-8-inch athlete was not tall enough to compete in that category.” “It is a 42,000-square-foot facility.”
7. Use numerals for the following:
- Ages: “2 years old”; “4-year-old child”; “in her 20s”
- Days of the month: “November 1, 2022”
- Time of day: “4:30 p.m.”; “10 o’clock”; “8 at night”; “9–11 a.m.”
- Years: “the 1980s”; “the ’90s”; “2022–2023”; “21st century”; “50 B.C.”; “Class of ’24”
- Degrees of temperature: “67 degrees”; “an 8-degree drop in just three hours”
- House numerals: “123 Evergreen Road, Apt. 2”
- Percentages: “3%”; “1-percentage-point difference”
- Proportions/ratios: “2-to-1 odds”; “1 in 6 students”
- Scores: “32–12 blowout”
- Votes and court decisions: “14–3 vote”; “5–4 decision”
- Speeds: “5 mph”
- Sums of money: “$8”; “2 cents”
- Course numbers: “Grammar 101”
- Mathematical usage: “3 plus 4 equals 7”; “3 + 4 = 7”; “multiply by 2”
- Rankings: “your No. 1 choice”
No. 1 Rule: Just Be Consistent
All style guides have subtle and not-so-subtle differences in how they approach numerals.
When someone hires us for business proofreading services, the Super Copy Editors team can adapt to any style a client chooses, or we can work with the client to create a new style that makes sense for a specific project.
The important thing is to stay consistent. If your style is slapdash, you’ll not only look sloppy but you’ll also risk confusing your readers.
Got a specific question about numbers that is not covered here? Leave a comment below, and I will do my best to help.
