Keyword density explained: how it is calculated and whether it matters

Keyword density is the share of a page's words taken up by a particular keyword: six mentions in a 600-word page is 1 percent. It was once treated as a ranking lever, but Google does not use a target density, and repeating keywords to hit a number is keyword stuffing, which is against its spam policies. The figure is still useful as a writing check, and that is how the keyword density checker frames it: a way to catch a page that never names its topic, or names it so often it reads badly.

How keyword density is calculated

For a single word, density is the number of times it appears divided by the total number of words, times 100. For a phrase, most tools count the words the phrase takes up: occurrences times the number of words in the phrase, divided by the total, times 100. So "running shoes" used 3 times in a 300-word page is 3 times 2 divided by 300, or 2 percent.

Small texts produce dramatic numbers. In the 12-word sentence pair "Running shoes for running. The best running shoes are light running shoes.", running appears 4 times (33 percent) and the phrase running shoes 3 times (50 percent). That is why density is only meaningful on full-length pages.

My checker counts every word in the total, then shows three tables: single words with common function words and words under three letters removed, and repeated two- and three-word phrases that do not start or end with a function word. Type a target keyword and it reports how many times the exact phrase appears and its density. It warns above 3 percent because, in my experience, repetition at that level is usually noticeable to a reader. That threshold is my editorial rule of thumb, not a number from Google.

Why it used to matter

Early search engines leaned heavily on the words on a page to decide what it was about, so repeating a term could lift a page in the results. Site owners responded with keyword-packed paragraphs, lists of town names, and hidden text in the same colour as the background, and rules of thumb about the ideal percentage spread through SEO advice. Search engines answered by giving more weight to other signals and by treating obvious repetition as spam. The percentage rules outlived the conditions that created them.

What Google says now

Google's own documentation is direct. Its SEO starter guide says that excessively repeating the same words is tiring for users and that keyword stuffing is against its spam policies. The spam policies define keyword stuffing as filling a page with keywords or numbers to manipulate rankings, often in unnatural lists or out of context, and give examples such as blocks of city names a page is trying to rank for. The same starter guide notes there is no magic word count, and that varying your wording naturally gives you more chances to match what people search for. Google also does not use the meta keywords tag. Nowhere does it recommend a density.

What the numbers are still good for

• Checking the topic is actually named. A page about running shoes that only ever says trainers or footwear may miss searches for the term people actually type.
• Catching accidental repetition. The phrase tables expose a line you have repeated in every paragraph.
• Spotting missing variety. If one term dominates and its natural synonyms never appear, the copy probably reads mechanically.
• Comparing drafts. The word frequency counter gives the raw list when you want to compare two versions.

Writing for topics, not percentages

Search systems today read for topics and meaning, not percentages. Start from the questions a reader brings to the page and answer them fully, using the words they would use. Cover the subtopics someone would expect, use synonyms and related terms naturally, and read the page aloud: if a phrase sounds forced, it is. Put the main term where it helps the reader most, in the title and the opening, and write a description that matches the page; How long should a title tag be? Pixels, not characters and How to write a meta description: length, structure, and when Google ignores it cover those, and the search snippet preview shows how they will look in results. Then check the prose with the readability checker, because clear writing serves readers and search engines alike.