What Is Keyword Density?

How Keyword Density Works

Keyword density is one of the oldest ideas in SEO, and it comes from an era when search engines were far cruder than they are now. In the late 1990s and early 2000s, ranking algorithms leaned heavily on counting: a page that mentioned “cheap flights” more often was assumed to be more about cheap flights. Keyword density formalized that assumption into a percentage, so SEOs could measure and tune it.

The trouble is that the assumption stopped being true. As search engines learned to read language rather than tally terms, frequency lost its power as a relevance signal. Today Google interprets a page with natural-language models — BERT and MUM among them — that judge meaning, context, and whether the page answers the query. A ratio of one word to the rest tells those systems almost nothing, which is why every credible statement from Google treats density as a non-factor. What remains real is the downside: cross the line into obvious repetition and you meet keyword stuffing, which Google actively penalizes.

Keyword Density Formula

The calculation itself is straightforward:

Keyword density = (number of keyword occurrences ÷ total word count) × 100

If the phrase “running shoes” appears 12 times in a 1,500-word review, its density is (12 ÷ 1,500) × 100 = 0.8%. Variations complicate it — do you count “running shoe” singular, or partial matches inside “trail-running shoes”? — which is part of why the metric is so slippery. The formula produces a tidy number that feels actionable and measures nothing Google rewards.

Example of Keyword Density

The clearest sourced answer comes from Google itself. In a widely referenced Google Search Central video, “What is the ideal keyword density of a page?”, Google’s then head of web spam Matt Cutts addressed the question directly. His answer was that there is no ideal figure.

Cutts explained the mechanism in plain terms: the first time you mention a word, it helps Google understand the page; a second mention can reinforce that; but once you keep repeating it, “it really doesn’t help that much more. There’s diminishing returns.” Push past that and, in his words, “you’re in danger of getting into keyword stuffing or gibberish.” He closed with the line SEOs have quoted ever since: “I would love it if people could stop obsessing about keyword density,” warning that anyone claiming a hard-and-fast rule “might be selling you keyword density software.”

That is the whole case in one clip. Density has a floor of usefulness — mention the topic so the engine and reader know what the page covers — and no ceiling of benefit, only a cliff of risk. The number itself was never the lever.

Keyword Density vs Entity Density

The two get muddled because both sound like “how often should I mention things.” But keyword density fixates on a single string, while entity density is about whether you have covered the concepts a topic genuinely involves — closer to semantic SEO than to a word-ratio dial. Neither is a target to game; only one points at something search engines still care about.

Frequently Asked Questions

The Bottom Line

Keyword density measures how frequently a phrase shows up in your text, and that measurement no longer buys you anything with Google. There is no percentage to hit and no bonus for hitting one. Cover the topic clearly, mention it as often as the explanation requires, and spend the effort you would have spent on ratios on saying something worth citing instead.