What is Correct Keyword Density %

Experience my friend.

I find 4% is the "sweet spot". Basically, if your keyword density if above 10%, you'll be flagged as a keyword stuffer. and keyword density above 15% is unreadable by humans... For example, if your main keywords (keywords you look to rank for) is dog-training, here is what 15% keyword density will look like.

"Dog-training can be tough if your dog-training techniques are outdated. Dog-training takes time and dog-training can be done by some who's dog-training techniques are well reputed. So, which dog-training strategies should a person use if someone has no dog-training experience? I can assure you that dog-training requires dog-training exercises on your part. Would dog-training be easier if you hired someone educated in dog-training?"

The above example is a good example of keyword stuffing. The best way to reduce the "keyword stuffing" is increase content. A good way to do that is to post articles on your site, about dog-training. If your site has a total of 15,000 words and you only have dog-training at a 4% density, your keywords are shown 600 times, which is pretty good compared to other "basic sites" in the same context.

Hope this answers your question to my reply.

-Edited to add a free tool-

http://www.webconfs.com/keyword-density-checker.php

^^ Free tool I use to check keyword density.