Rules for Writing Numbers for your CP Editorial
1. Spell small numbers out
The small numbers, such as whole numbers smaller than ten, should be spelled out.
2. Don’t start a sentence with a numeral
Make it “Fourscore and seven years ago,” not “4 score and 7 years ago.” That means you might have to rewrite some sentences: “Fans bought 400,000 copies the first day” instead of “400,000 copies were sold the first day.”
3. Centuries and decades should be spelled out
Use the Eighties or nineteenth century.
In formal writing, you should spell the percentage out like “12 percent of the players” or 86 percent of the population
5. If the number is rounded or estimated, spell it out.
Rounded numbers over a million are written as a numeral plus a word. Use “About 400 million people speak Spanish natively,” instead of “About 400,000,000 people speak Spanish natively.” If you’re using the exact number, you’d write it out, of course.
6. Two numbers next to each other.
It can be confusing if you write “7 13-year-olds”, so write one of them as a numeral, like “seven 13-year-olds”. Pick the number that has the fewest letters.