Yes, there's plenty of tools that can do this (Surfer SEO/Neuron Writer/Frase/Clearscope). The problem with them is everyone who uses them all become average. SERPs aren't static and change often. What might look like a good keyword density based on top ranking sites today might change next month or after a Core Algorithm update. Keyword density is not as important as where you place the keyword. I don't bother looking at any of that anymore and use Google's NLP to score my article against competitors.
Several online tools can help you analyze keyword density: The HOTH’s Free Keyword Density Checker Tool: Instantly analyze keyword usage on a page. Wordily’s Word Density Checker: Analyze keyword frequency in your text. Small SEO Tools: Offers an easy-to-use keyword density tool.