Most writing style guides advise against using a percentage sign at the beginning of a sentence. AMA, APA, and MLA academic writing styles state you should spell out numbers and the word “percent” at the beginning of a sentence.
However, the rules shift if you insert a percentage within the middle of a sentence. In these cases, you should use the numeral and the percentage sign. Here are some examples.
Standards for Beginnings of Sentences
Let’s say you want to quote a statistic to back up your arguments in an academic paper. You learn that 75% of college students have financial difficulties after graduation.
Here’s how you need to write about the statistic if you lead a sentence with it. “Seventy-five percent of college students experience financial struggles after graduation.”
The standard also applies for numbers that are above nine. Typically, most style guidelines say you should write out numbers zero through nine as words. And you should write numbers 10 and above in numeric form.
Using a number at the beginning of a sentence is the exception. Always spell numbers out as words, regardless of value.
Writing Rules for Ends of Sentences
So, what about writing percentages at the end of sentences? Fortunately, the rules are easy to remember because they’re the same as they are for the start of sentences.
Let’s say you wanted to structure the sentence about college graduates with the statistic at the end. You would write it similar to this: “The number of college graduates that run into financial problems after graduation is seventy-five percent.”
Other Sentence Placements
If you’re not inserting a statistic at the end or beginning of a sentence, you can use the percentage sign and numeral. A hypothetical example is “Approximately 50% of women over the age of 40 have uterine fibroids.”
Although AP style guides formerly advised against the use of the percentage sign anywhere in a sentence, the practice is now okay.
Always Check Style Guides
Style guides often include variations in writing rules. Before you write, you need to check the style guide your university, press outlet, employer, or journal requires. Make sure you refer to the latest edition, as standards can change from one year to the next.
Under most circumstances, you can’t start a sentence with a percentage sign. Instead, you need to write out the word percent and the number as a word.