As mentioned on the homepage the (Not Provided) Estimator has the ability to:
Two features within the Keyword Density Tool that can be utilized to achieve more accurate results are options that can be selected right under the URL bar within the page; "Don't count common words" and "Use weighted keywords".
By selecting "don't count common words", you eliminate unimportant transition words like "and" "the" "of" "for" etc., from being included in the word count. By selecting "use weighed keywords" the tool makes sure that keywords used within headers (H1, H2, H3) and titles are weighted heavier than keywords used within the body of the text. The tool counts words in headers as up to 3X heavier than words in body text. The word will be repeated at the end of the "Analyzed Content" text multiple times to help mimic how Google would feel and react to this word if it was found in a header title versus a paragraph.