Gunning Fog Index calculator
The Fog Index estimates the years of formal education a reader needs to understand a text the first time through. “Complex words” are words of three or more syllables, not counting proper nouns, familiar compounds, or words that only reach three syllables through -es, -ed or -ing endings.
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The Gunning Fog Index formula
0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
Gunning suggested that anything above 12 is too hard for most people. Popular magazines tend to sit around 8 to 10.
Robert Gunning, an American businessman who consulted for newspapers, introduced it in his 1952 book “The Technique of Clear Writing”.
What your score means
| Score | Reading level |
|---|---|
| 6 | Sixth grade – very readable |
| 8 | Popular fiction, tabloid news |
| 10 | Typical magazine |
| 12 | Upper limit for wide audiences |
| 14 | College sophomore |
| 17+ | Graduate level |
Drag the inputs, watch the score
The formula only “sees” these numbers. Change them and notice which one moves the score most.
Grade level (higher = harder)
12.0
US grade 12
Questions people ask
What is a good Gunning Fog score?
Below 12 for a general audience; 7 to 8 is ideal for broad readability. Technical documents often reach 14 to 18.
What counts as a complex word?
A word with three or more syllables, excluding proper nouns, hyphenated compounds and words that only reach three syllables through a -es, -ed or -ing ending. “Important” is complex; “created” is not.
Why is the Fog Index higher than my Flesch–Kincaid grade?
The Fog formula penalises each three-syllable word heavily, so vocabulary-dense writing scores higher under Fog than under Flesch–Kincaid, which averages syllables across all words.