What keyword density tells you
Keyword density is how often a word or phrase appears compared with all the words on the page. It's a quick way to see what a page is really about, and whether the phrase you want to rank for is actually there.
There's no magic percentage. If a phrase reads naturally and appears in the title, the main heading and the first paragraph, that's usually enough.
Keyword stuffing
Repeating a phrase unnaturally (for example above 4–5% of all words) reads badly and can hurt rankings. Use related words and answer follow-up questions instead.