Keyword density is a percentage

The keyword density of a piece of content is the number of keywords compared to the number of other words in a piece of content. It’s usually expressed as a percentage, so for example if a 100-word piece has three instances of the keyword ‘dogs’, the keyword density is 3%. Note that the number of words in the keyword affects the density as well, so for example if the keyword was ‘dog food’, the keyword density is 6%. It is thought that Google and the other search engines measure keyword density and have a filter if the density is over a certain limit. This may be why the SEO industry talks about density, but it isn’t helpful from a site owner’s perspective.