Friday, November 11, 2011

How to Write Percentages

I was editing a document that talked about percentages the other day and realized that I had made an assumption about the rules for percents—that is, that they are the same as the rules for temperatures (which I covered in How to Write Temperature Degrees).

So I hurriedly did some digging and discovered—bum ba dum!—my assumption was accurate! Or, at least, accurate enough that if you can remember and apply one, you can remember and apply both without anyone besides the Grammar Nazis criticizing your work.

Percentages in Informal Writing

Anything goes in informal writing—just remember to be consistent. Choose the symbol (%) or choose to write it out (percent)—choose numbers or choose numerals—and stick with it. My trusty MLA Style Guide points out, however:
Note that percent is not interchangeable with the noun percentage (1 percent is a very small percentage). Note also that no space appears between the numeral and the symbol %.

Percent Symbol Keyboard Shortcut

The powers that be consider the percent symbol relevant enough to our daily lives that it is on the keyboard and doesn't require a special shortcut. On most keyboards, you'll just need to push shift + 5.

Percentages in Formal Writing

The biggest difference here between writing temperatures and writing percentages is that there is one less sub-rule to remember for percentages.

The Numeral
Percentages are always in numerals, whether using the percent symbol or writing out the word, and whether in scientific material or in nontechnical material.
He loves her 9 percent of the time. 
Women think about problems 90% more often than men do.

The Percent Symbol
The percent symbol is always used in scientific material and can be used in nontechnical material if it talks a lot about percentages.
The monkey shares 95% of its DNA with gorillas. 
Sears is having a 50% off everything sale, Dillards is having a 33% off everything sale, but JC Penney is having a 75% off everything sale! 
According to a recent survey, 19 percent of Americans give over $100 a year to charitable organizations.

Percentages in AP Style

Once again, AP style must do its own thing. Percentages in AP style are always in numerals and percent is always spelled out.
The coach told the reporters, "Our team is giving 110 percent!" 
Genes dictate about 70 percent of an individual's personality.


  1. Actually, this is not true. In a "scientific context" the symbol is used. Otherwise, it is spelled out. (I guess it's up to you to figure out what constitutes a scientific context).

  2. What if it's at the end of a sentence.