Rapid Writer has the capacity to measure your keyword density.
Again this was a tool used when keyword stuffing was the norm and Google was beginning to penalise the overuse of keywords.
As you can see from the screenshot it is easy to highlight your chosen keyword (here for lack of originality I have selected the word 'keyword' as my keyword.)
Simply highlight the text and the density figure will appear on the right hand side - here 4.3%.
One thing to watch with this tool is that it is an exact match tool, so any versions of your keyword such as plurals will need to be calculated separately - as I have shown here below.
Measuring Keyword Density In Normal Blogs
Rapid Writer doesn't just have to be used for mini blogging, even in your normal blogging writing there can be a moment of panic when you wonder am I using this phrase too often.
You can simply copy your text into the rapid writer and run a keyword density check.
So what use is this tool for mini bloggers? Well read on ......