Gunning Fog Readability Formula

The Gunning Fog readability formula calculates the U.S. grade level of a text sample based on its number of sentences and complex words (i.e., words that contain three or more syllables).

Note that numerals are always ignored for this test, so Readability Studio always ignores your numeral syllabication setting when calculating it.

The Gunning Fog Formula

GL = .4*(W/S+((SYW/W)*100))

Where:

GL	U.S. grade level
W	Number of words
SYW	Number of 3+ syllable words
S	Number of sentences

Citations

Gunning, R. (1952). The Technique of Clear Writing.