Sugarman's Fog Index (Free Calculator)
Just found this resource today - a free "fog index" calculator:
Gunning Fog Index Calculator
I first heard about this in The Adweek Copywriting Handbook where Sugarman states:
"Robert Gunner... created the Fog Index for newspaper writers to help them avoid so-called foggy writing and determine for themselves the grade level of the copy they were writing. In short, were they writing with enough clarity so that a fifth grader could understand their copy or must a reader be in high school or even college to understand it? The lower the grade level, the wider the audience."
To give you an idea, best-selling books are written for 8th to 10th grade levels and that's probably a good grade to aim for with your sales copy.
Anyway, fun thing to test on your own copy
Cheers,
David
"Sell the Magic of A Dream"
www.DP-Copywriting-Service.com