Percentages show up everywhere: exam results, discount labels, survey reports, and bank interest rates. Yet many people hesitate when they have to write them in words, especially on formal documents where figures alone are not enough.
The basic rule is simple. Write the number in words, then write the word percent. Fifty percent, seventy-five percent, one hundred percent. The percent sign becomes the word percent, and the number follows the same spelling rules as any other number: hyphenate compound numbers from twenty-one to ninety-nine, and use and only where your style guide asks for it, as in one hundred and twenty-five percent.
Ratios work the same way, with the word to standing in for the colon. A ratio of 3:2 becomes three to two. A classroom ratio of 5:1 becomes five to one. Keep the order of the numbers the same, and do not swap in words like versus unless the document actually means a contest.
Scores and marks need a little more care. A test score of 87 out of 100 becomes eighty-seven out of one hundred. A cricket-style score or a grade like 9/10 becomes nine out of ten. Writing the full phrase avoids the ambiguity of a bare slash, which readers can misread as a date or a fraction.
Fractions of a percent deserve attention too. Twelve and a half percent is the natural way to write 12.5 percent in words, and nought point five percent works for 0.5 percent in British usage. Avoid mixing digits and words in the same phrase, such as 12 and a half percent written half in figures, because that inconsistency is exactly what examiners and bank clerks flag.
When should you write percentages in words at all? On cheques, legal forms, and exam answers, words protect against tampering and misreading, which is why amounts are spelled out in full. In casual reports and slides, figures are fine. The safest habit is this: if the document matters, spell it out, and check your result against a free numbers-to-words converter at https://wordsfornumbers.com/ before you submit it.
Three quick checks will keep you safe. First, read the sentence aloud: if it sounds awkward, the wording is probably wrong. Second, confirm hyphenation in compound numbers. Third, keep one style through the whole document, so you never write fifty percent in one paragraph and 50 percent in the next.
