- For Teachers The resulting number is your Gunning Fog Index.
The Gunning Fog Index gives the number of years of education
that your reader hypothetically needs to understand the
paragraph or text. The Gunning Fog Index formula implies that
short sentences written in plain English achieve a better score
than long sentences written in complicated language. For
reference, the New York Times has an average Fog Index of 11-12,
Time magazine about 11. Typically, technical documentation has a
Fog Index between 10 and 15, and professional prose almost never
exceeds 18.