Fog Index Calculator
It calculates the Gunning Fog Index for a piece of writing.
The Gunning Fog Index is a simple method for judging the reading level that is required to comprehend the writing. The higher the Fog Index the trickier it is to read. Basically, the Index score indicates the number of years of schooling required to understand the text...
Er. Try a shorter piece. It works for 3,000 words. You shouldn't need more than a few hundred really, but more words will smooth out possible imperfections in the algorithm.