Numbers

Q. In prose, when writing percentages, which is correct: 10 percent; ten percent, or 10%?

A. Chicago prefers the use of numerals for all numbers used as part of percentages, but use the word “percent” for humanistic copy and the “%” symbol for scientific and statistical copy:

humanistic:

10 percent (but spell out “10” if it begins the sentence)

scientific, statistical:

10%

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]