Fun fact #1: I have three brothers.
Fun fact #2: I can provide 54,378 reasons that my brothers get under my skin.
You may have noticed while reading the above examples that I spelled out the number three and used the numeral form to write 54,378. Why did I use the whole word for the former, and the numeral form for the latter?
While the answer usually depends on the style of writing you’re using (for example, MLA, AP, APA, or Chicago), there are some general patterns to fall back on when you’re stuck. This article will outline when to use the numeral form of a number, and when to use the spelled-out word form–let’s dive in.
General Rule for Each Style Guide
Depending on your writing context, subject, or genre–for example, science report, newspaper article, movie review, blog post, fictional narrative–you should consult the appropriate style guide to determine how to format the numbers in your writing. Each style guide outlines a unique set of rules for various situations, including how to appropriately format in-text numbers.
Below, find the general rules for spelling out numerals in various style guides.
APA and AP Style: Spell out numbers from zero to nine, and use numerals for every number 10 or greater. (In the case of this article, I am using the AP Style Guide.)
Example: I have eight minutes until my bus arrives.
Example: The band’s drummer played a 19-minute drum solo.
Chicago and MLA Style: Spell out numbers from zero through one hundred, and use numerals for every number 101 and over.
Example: The old man climbed twenty-eight flights of stairs to reach the rooftop.
Example: My band has written over 150 songs.
Spell out small numbers, use numerals for large numbers.
As a writer, you want to make your language as clear as possible for your reader. Small numbers, containing between one and three syllables, are familiar and easily digestible for the reader.
By spelling out these small numbers, we maintain a consistent style in our language without compromising readability.
Small number (correct): I have seven pets.
Small number (incorrect): I have 7 pets.
Numbers over 100, on the other hand, get lengthy and complicated. Since these numbers have over five syllables, the reader has to work hard to decode the number–simply using numerals makes the visual much more understandable.
Large number (correct): There are 376 primate species in the world
Large number (incorrect): There are three hundred and seventy-six primate species in the world.
General Rules for Spelling Out Numbers
The following rules apply in nearly every case, so you can use them as default across tasks, genre, or style guides.
1. Keep a consistent pattern for using numerals and spelling out words.
Make sure to remain consistent with which numbers you spell out and which ones you format with numerals. This will avoid confusing your reader, preventing them from thinking you changed the formatting to distinguish the numbers in some way.
Consistent: I have eighteen hours until I take my final exam, which means twenty-one hours until spring break.
Inconsistent: My team had seventy-eight points in the game, and I scored 21 of them.
2. If the number begins its sentence, spell it out.
For stylistic purposes, always spell out a number that begins a sentence–even when the number is above 100 and you would otherwise use numerals for it.
To maintain consistency with numeral usage, you might restructure the sentence so that a numeral does not place at the beginning.
Correct: Five hundred and seventeen new students joined our school this year.
Incorrect: 517 new students joined our school this year.
Correct, reformatted: This year, 517 new students joined our school.
3. Use numerals for all decimals, percentages, and mixed fractions; for regular fractions, use numerals or hyphenated words.
Since decimals, percentages, and mixed fractions can get complicated and wordy, always use numerals to indicate these numbers.
Decimals:
Correct: NFL wide receiver Tyreek Hill ran the forty-yard dash in 4.29 seconds.
Incorrect: I earned a four-point-seven GPA in high school.
Percentages:
Correct: Among NCAA collegiate athletes, only 2 percent make it to the professional level.
Incorrect: The global rate for handwashing after using the bathroom is under twenty percent.
Mixed fractions (whole number plus a fraction):
Correct: Last night I had 3 ½ slices of pizza.
Incorrect: Last night my dad ate four and a half slices of pizza.
For regular (non-mixed) fractions, you can either spell the word out or use the numerals. However, for common fractions (one-half, two-thirds, three-quarters), it’s best to spell out the words and use a hyphen to connect them.
Common fractions:
Correct: Surprisingly, one-third of all adults sleep with a comfort object, like a teddy bear.
Incorrect: Fewer than 1/4 of Americans meet the recommended guidelines for physical activity.
4. For round large numbers (those ending with “hundred,” “thousand,” “million,” “billion,” etc.), use standard formatting for the initial non-zero number, followed by spelling out the mass quantity.
When formatting a rounded large number, such as four hundred, five thousand, 36 million, or ten billion, format the initial non-zero number as you would any other non-zero number using your style guide’s conventions. Then, spell out the large, rounded number that follows: hundred, thousand, million, billion, etc.
Correct:
- The earth is 4.5 billion years old.
- Michael Jordan scored over 32 thousand points in his career.
- The rent in San Antonio averages around nine hundred dollars per month.
- There are 86,400 seconds in a day, and I think about you during each one.
Incorrect:
- Austrolopithecus lived around 3,000,000 years ago.
- The world contains around 10,000 cities.
- One famous song in the musical Rent lists the length of a year: five hundred twenty-five thousand six hundred minutes.
5. Hyphenate compound numbers between twenty-one and ninety-nine.
Hyphenate spelled-out compound numbers, which are all those between twenty-one and ninety-nine. This rule applies even when these compound numbers exist within larger numbers (seventy-six million; seven hundred and forty-two).
Do not hyphenate larger numbers (seven million, eighteen billion, three hundred).
Correct: The National Football League has thirty-two teams.
Incorrect: Major League Soccer has twenty eight teams.
6. Always use numerals for sums of money, ages, dates, and time
As a matter of style and audience expectations, sums of money ($75), ages (23 years old), dates (February 14, 2022), and time (4:14 p.m.) always use numerals. Additionally, references to years and historical time periods (decades, centuries, etc.) always take a numeral form.
Sums of money:
Correct: My allowance is $25 per week.
Incorrect: Unfairly, my brother gets thirty dollars per week.
Ages:
Correct: My grandpa is 87 years old.
Incorrect: Oscar Swahn was seventy-two years old when he competed in the Olympics.
Dates:
Correct: My mom was born on March 4, 1966.
Incorrect: I was born on May seventeenth, nineteen ninety-two.
Historical references:
Correct: The kingdom of Abyssinia took over Ethiopia in the year 1270.
Incorrect: The modern nation of Turkey was founded in nineteen twenty-one.
Time:
Correct: My last class on Thursday ends at 7:50 p.m.
Incorrect: My earliest Monday class begins at eight in the morning.
When in doubt, consult the style guide and stay consistent.
There’s really only one major difference between the style guides: if you use numerals or whole words to format the numbers between 11 and 100. Your writing task should determine which style guide you consult to navigate this formatting decision, and for the rest of your number-formatting concerns, remember this: consistency is key.
The most important part is to stay consistent so as to not throw off your readers. Still, there are some common conventions (listed in this article) that will help you capitalize on audience expectations and submit the most professional piece possible.
When you feel stuck, this guide will be here for you. Enjoy the process, and as always, write on.
