There are so many rules–and so many different style guides with their own unique sets of rules–that I’m only going to address one today: AP. This post gives you the lowdown on the AP’s guidelines for writing out numbers versus using numerals.
But, wait! You don’t have to follow a particular writing style? Lucky you. Still, you need to be consistent in your use of numbers and numerals, so it helps to pick a style and stick with it. Consider the following guidelines. First, let me warn you: There are many rules and many, many exceptions.
Let’s start with the rules:
- Write out all single-digit numbers (i.e., one through nine)
- Write all double-digit numbers as numerals (i.e., 10–999,999)
And just so we’re clear, this could leave you with some wonky-looking sentences:
- Angelica has 10 three-room houses.
- I think the Lopez family owns seven to 12 dogs.
- Pete has been living in the Midwest for a five- to 10-year period.
Now onto the exceptions:
There are literally so many that I’ll just mention the biggies:
- Ages. They’re always written as numerals: 5-year-old boy, she’s 75 years old, etc.
- Million, billion and trillion are always written as words and always used with numerals: 1 million, 15 billion, etc.
- Distances are always numerals: 10 miles from here, 2 kilometers away, etc.
- The first word in a sentence should never be a numeral, unless it’s a year. Ex. One-thousand cats walked the city streets that day. But: 1998 was a wonderful year.
OK, if you’ve gotten to the end of this post without pulling out all your hair, I commend you. Now, if you have to follow AP style, you need access to the online or print style guide–the rules are too nitpicky to memorize.
Alternately, you can shoot me an email. I work with AP every day, so I’m pretty knowledgeable. Hashtag humble brag.