Self-Editing Tips: Chicago Style Overview of Number Rules

Colorful blocks of different shapes with numbers.

Everyone comes to writing with a different background. Different instructors. Different books we’ve read over the years that influence us. Different advice we’ve been given and rules we’ve been told. But when it comes to writing for yourself as a self-published author or prepping a manuscript for traditional publication, you may need to go against the rules you thought you knew and adapt to one style guide or another.

What are style guides?

Style guides are standardized sets of rules that writers can follow to make their manuscripts consistent internally and with other books that may be their competition.

The most common style guide in commercial book publishing is the Chicago Manual of Style (which is currently in its 17th edition), but many publishers make their own in-house style guides that deviate from the general rules.

What Style Guide Should I Use?

In most cases, whether you’re self-publishing or submitting for traditional publication. The CMoS guide is a great place to start. Of course, if there’s a rule you don’t like and you’re self-publishing, you can make your own rule! Just be sure to apply the rule consistently throughout your writing and to let your editor know about your preference.

Deviating from the Style Guide

For example, CMoS typically defers to the Merriam-Webster dictionary for spellings of words, however, I recently edited for an author who preferred the lesser-used spelling of “advisor” instead of the M-W preference “adviser.” By making me aware of his preference, I was able to help him make sure that his preferred spelling was maintained.

Other examples of deviating from CMoS that I’ve seen include a preference for “healthcare” over “health care” and maintaining capitalization for holy and religious terms that CMoS defaults to downcase.

Numbers in CMoS

Every style guide starts with a general rule, then specifies more details depending on the specific use and situations a writer might find themselves in.

The General Rule

In CMoS, the general rule is to spell out numbers of one hundred or less. Hyphenate numbers that are two-word phrases.

Additionally, you use the numeral for 101 and higher.

Ex:

He is seven years old. 

We expect ninety-five visitors. 

After 112 years had passed, the house no longer stood tall. 

Some Notable Exceptions

Numbers that begin a sentence

Spell out numbers that begin a sentence, even if it’s a year or large number you would normally use a numeral for. Do not begin sentences with numerals.

Ex: 

Eighteen seventy-five was a memorable year.

Two million dollars was the largest donation. 

To avoid this, if you’d rather use the numeral, add wording to the start of the sentence.

Ex: 

Instead of “1875 was a memorable year,” rephrase to:

In 1875, memorable events occurred…

Large numbers

When writing whole numbers in the ten thousands, hundred thousands, millions, or billions, spell out the number

Ex:

We expect ten thousand people to attend the event. 

After one hundred and forty thousand years, the tectonic shifts made the area unrecognizable. 

No fewer than four million results were compiled. 

Money

When writing monetary amounts, use the dollar symbol ($) and the numeral, or a combination of numerals and spelled words in the case of large numbers, rather than writing out the number and the word “dollars.” There is no need to specify “USD.” If using another monetary denomination (euros, rupees, yen, etc.), use the appropriate symbol. If referring to a non-US monetary unit that also uses “dollars,” you may specify the country with a designation before the dollar symbol. 

For example, Canadian dollars are expressed as “C$”, and Australian dollars are expressed as “A$”.  

Ex:

“Hey!” I cried. “You owe me $5!”

On sale this week only for £999.

The average cost of a house in the city is $175,000. 

The facility is expected to generate more than C$2 million annually.

Time

For times, choose between either the specific “a.m.” or “p.m.” designation or a word phrase to describe time — such as “in the afternoon” or “o’clock.” 

For a.m. and p.m., use the numeral and with word phrases, spell out the number.

When precise time is required, use a.m. and p.m.

Ex: 

The package arrived at precisely 4:22 p.m.

The package arrived around four o’clock.

The package arrived at approximately four in the afternoon.

Measurements

OK, so this gets tricky: when using an abbreviation for the unit of measurement, use a numeral. But spell out numbers when measurements are spelled as words.

Ex:

We need a board that’s twenty-two inches long.

We need a board measuring 22 x 4 in.

Dates

You can pretty much always expect to use the numerals when including the entire date. When writing more narratively consider spelling out numbers, especially for ordinals.

Ex:

They will arrive on June 2, 2022.

They will arrive on June second.  

Percentages

In nontechnical manuscripts, CMoS prefers spelling out the word “percent” rather than using the percent symbol (%). 

Ex: 

This year’s turnout was twenty percent higher than last year.

There was an increase of 217 percent over last year.

I only scored forty-five percent on the exam. 

How to Self-Edit for Number Corrections

While writing your draft, chances are that you didn’t have all these number rules in mind. Even if you were mindful of being compliant with Chicago style, the best writers sometimes make mistakes. Once you are ready to put your manuscript through a self-editing checklist for authors, I suggest that one of those rounds of self-editing focus specifically on number rules. 

There are two main ways you can make mistakes with numbers while writing: either you used the numeral where you should have spelled out the word, or you used the word where you should have used the numeral. 

To correct numerals to words

Using CTRL+F, search for all the numerals in your text to confirm that they should be numerals. 

To search all numerals, put the following into your search bar: 

^#

This should highlight every numeral, and you can use the navigation panel on the left-hand side of the screen to check that each one is correct.

To correct words to numerals

This is a bit trickier but can still be completed using CTRL+F. 

You will need to search for each number-word individually, at least for one through twenty. (One, two, three, four…etc.) 

Once this is complete, search for the root denomination word of each count of ten. (Twenty, thirty, forty…etc.)

Correct "dollars" to $ and "%" to "percent"

Lastly, you can perform separate searches for the word “dollars” (or other monetary units) and for the percent symbol (%) to find any use of them in the text, then make corrections by spelling out the word instead of using the symbol. 

Nice work! You've successfully self-edited your manuscript for numbers!

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