Keyword Density - The fact and the fiction

One of the most important aspects of optimizing your site for search engines (SEO) is your web copy. Google and the other search engines read the words on your page to figure out what your site is about and which searches they should display it in.

But they don’t read like humans. We actually make sense of the individual words and their combinations, (phrases, sentences, paragraphs, pages, page hierarchies, etc). We even take visual design and aural elements into account.
Search engines aren’t that sophisticated (even Google!). In fact, they don’t really process meaning at all; they categorize a site’s subject matter based on the words that are used most often in the body copy, headings, links, etc. The logic behind this behavior is that if a site is about widgets, the word “widgets” - and similar words - will naturally appear in these places at quite a high frequency. (That’s a little simplistic, but it’s about as much as most of us need to know about how search engines work. Their indexing algorithms involve incredibly complex maths - more than my little brain can handle! Learn more about how search engines evaluate content.)

So if you want your site to appear in the search results for “cheap glazier”, then you’d use that phrase relatively often throughout your site. This is known as ‘keyword density’. Simply put, keyword density is a measure of the number of times your keyword appears on a page expressed as a percentage of the total wordcount of that page. For example, if your page has 100 words, and your keyword phrase appears 5 times, its density is 5%. (Here’s an easy-to-use keyword density calculator.)

Keyword density is a particularly problematic concept, mostly because people place great emphasis on it, when, in fact, the search engines don’t measure density like that at all. So when you hear all the rules about what density you should be aiming for, always bear that in mind. Don’t start thinking that the search engines are looking for a density of 5% or 3% or 10%; they’re not. Just use density calculations as a yardstick. A density of 3% will give you a page with plenty of instances of your keyword. If you can’t get a density that high without impacting readability, settle for a lower density. The important thing is that you use your keywords more often than any other single word or phrase.