Keyword densities really are not rocket science, so don’t fall into the trap of making things more complicated than they need to be. Go to Google and search on "keyword density." The first three pages should be ones that provide about 20 or 25 different tools for calculating KWD.
Now all you have to do is pick one that feels user-friendly to you and use it to optimize your web page, noting the results. Now try something else: run a Google search on your keyword, and run the analysis on the first ten sites. Take a good hard look at the results. From this, you should get a good idea how your page will compare with the ten top ranking pages in Google, at least in terms of keyword density.
Here’s the thing that frustrates people, though: if you go and do that with three or four different KWD tools, you will no doubt come up with different numbers, but the graph of those numbers will look very similar. Don’t worry about it, because the numbers aren’t the most important thing. You only care how they compare to each other.
Something else you'll probably discover is that keyword density is not a very good indicator of rank. The top ranking page may have a much lower density than the page at number ten, for example.
Why does this happen, when you work so hard to get your keyword density high? It happens because KWD is only one factor among many. It's important to a good ranking, but it's not the be-all and end-all of a good ranking. What you really want to know from your analysis is the range of density values that rank well. Chances are good that if your page is below that range, getting on page one to compete with the big dogs will be tough, and if you're above that range, the search engines may think you’re “keyword stuffing” and you’ll be penalized. Just remember, though, the numbers are guidelines you should know, not carved-in-stone rules that forever define your fate. Experiment!
You may hear self-proclaimed website gurus say that keyword density should always run between two and eight percent or whatever the current numbers being quoted in forums across the Internet happen to be. That’s partly true. Those numbers are probably fairly accurate for most keywords. They’re based on averages and it’s always good to stick close to an average.
But there’s a problem. Here’s how the problem goes: the most commonly used letter in English is the letter “E.” If you wrote a ten word sentence, it would be much easier to use the letter E five times in that sentence than it would be to use, say, the letter Z five times. Letters aren’t an even distribution. Neither are keywords. Big shock, huh?
Remember what I said earlier about not sounding awkward in your content? Well, the biggest thing about keyword density is that it must read well and sound very natural to a user. It’s useless to get a page one ranking if your content is very lame. Like the letter E, some keywords are easy to use a lot of while still sounding natural. For instance, if your keyword was “grass” on a site about lawn care, it wouldn’t be hard to use “grass” a lot.
But some keywords just don’t lend themselves to being used a lot—like “quince.” (It’s a type of fruit.) Here’s the choice to be made: you can use an average range, which will work well most times, or you can spend time analyzing the top ten pages to find the best range for that particular keyword and be sure you're not trying to optimize for a Z or a quince.
Frustrated? Don’t be! It isn’t that hard. If you’re still confused, check out a competitor's page in Google's cache (which highlights the keywords for you) to get a good visual feel for density.
Another good tip is to perform a “real person sanity check” on your content. Reading your optimized content out loud several times, and try to get a natural flow that will make the copy draw users who will come back. Then take a hard look at your content. If you can substitute a keyword for a pronoun without loosing your flow, do it.
For instance, if your keyword is “hammock”, instead of a sentence saying, “I love to lie in it,” say, “I love to lie in my hammock.”
