Keyword Density - Is it Important?
Keyword density = The number of times a keyword is used on a web page divided by the total number of words on the page.
Optimum keyword density all depends on the competition of the search term you are targeting. Anything from 3-10% is usually recommended, although most SEO professionals argue that keyword density is not as relevant as people will have you thinking. Google certainly pays more attention to which keywords you have optimised your title tags for. So for example the first 4 keywords used in your title tags should be the keywords you are optimising the relevant page for.
Don't obsess about keyword density
Instead of obsessing about keyword density use your most important keywords in page titles, bold text, H tags (headings), site maps and anchor text on your site.
If anything keyword density is taken more so into consideration when a page has been heavily stuffed with keywords. A keyword density above 30% is too much. Basically if you have too much keyword density, Google and others can consider this spam, and may penalize your site.
I use SEO Chats Keyword Density Tool to check if a keyword is repated too much on a page