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%