The key to a professional writing project is consistency. Because we can spell or write out numbers, it is important to pick a numbering convention before you begin writing or during the editing phase.

When you’re preparing to publish, every detail matters.

While authors give grammar and spelling a lot of attention, smaller details, such as number usage, can be forgotten. Opinions on when to write out numbers vary from author to author. Of course, academic papers are typically required to follow a particular style guide. These style guides (AMA, APA, AP, CMS, MLA, Turabian, and others) lay out very specific rules on number usage.

When there is no style guide to follow, such as in fiction and non-fiction works, number usage boils down to one essential concept. Consistency. “Minor” details such as consistency of number usage are what publishers look for to determine if your project is professional—and therefore, publishable.

When to Write Out Numbers

Here are some common number usage conventions seen in academic, fiction, and non-fiction projects:

Write Out Single-Digit Numbers

Of the 150 people at the party, one is 18 and three are 35 years old.

Write Out One- or Two-Digit Numbers

Of the 150 people at the party, one is eighteen and three are thirty-five years old.

Write Out One-Word Numbers

Of the 150 people at the party, one is eighteen and three are 35 years old.

Write Out Two-Word Numbers

Of the 150 people at the party, one is eighteen and three are thirty-five years old.

Write Out All Numbers

Of the one hundred fifty people at the party, one is eighteen and three are thirty-five years old.

As mentioned earlier, it is important to choose one style and stick with it. Depending on the numbering convention you use, a few more standard rules may come into play. Some of these rules are required by style guides, while others are just common conventions.

Beginning of a Sentence

It is often frowned upon to use numerals at the start of a sentence. If possible, reword the sentence so it begins with a word. Otherwise, write out the number.

Seven thousand nine hundred sixty-two people live here.

or

The population is 7,962.

When to Write Out Numbers

Back-to-Back Numbers

When numbers appear one after another, it is common to write out one of them and use numerals for the other to improve readability.

There were 20 twenty-three-year-olds.

or

There were twenty 23-year-olds.

Dialogue

When writing dialogue, it is best to write out all numbers and symbols. This way there is no question as to how the number is pronounced.

He said, “I have two thousand two hundred dollars.”

or

He said, “I have twenty-two hundred dollars.”

not

He said, “I have $2,200.”

Normalization

Another exception to the rule is when two numbers appear in the same sentence. For this example, let’s assume you have been writing out all single-digit numbers. If you are writing a sentence that includes several numbers, and you would usually write one of the numbers as a numeral, use numerals for all related numbers in the sentence.

I have three sons. They are 1, 3, and 11 years old.

but

I have three children. They are one, three, and six years old.

Conclusion

These may seem like minor details at first, but a consistent numbering convention proves to publishers how experienced you are. Details such as this are the key to establishing yourself, and the reason editors are so necessary.

Originally posted 6/18/2015 and happily updated 10/25/2017. Thanks for reading!

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