Gunning Fog Index calculator

The Fog Index estimates the years of formal education a reader needs to understand your text on first reading.

Text to score

Average grade level

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Paste at least a few sentences.

Words0
Sentences0
Syllables / word0.00
Words / sentence0.0
Complex words (3+ syllables)0%

Readability scores
Formula	Score	Meaning
Scores appear here as soon as you type.

Clear the fog

Complex words are those with three or more syllables. Swap them for plain words and watch the index drop.

Tap a highlighted word to swap it for a plainer one.

The will each and the to every . We that may be . Please us if you have questions.

Gunning Fog index

20.9

Words28
Sentences3
Complex words (3+ syllables)12

0.4 × (9.3 + 100 × 12/28)

The Gunning Fog formula

0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]

Robert Gunning, an American businessman who consulted for newspapers, published the index in 1952 in “The Technique of Clear Writing”. A “complex word” has three or more syllables, not counting proper nouns, hyphenated compounds, or common endings like -es, -ed and -ing that push a word to three syllables.

Reading the score

Fog index	Reading level	Example
6	Sixth grade	Comics, simple instructions
8	Eighth grade	Popular fiction, Reader’s Digest
10	High school sophomore	Time, Newsweek
12	High school senior	The Wall Street Journal
14	College sophomore	Academic textbooks
17+	College graduate	Specialist or legal writing

Target

Gunning suggested that text for a wide audience needs a Fog index under 12, and text meant for near-universal understanding under 8.

Questions people ask

Is the Gunning Fog Index accurate?

It’s a rough guide. Not every long word is hard (“banana”, “interesting”) and some short words are obscure. It’s best used to compare drafts of the same text.

How is it different from Flesch–Kincaid?

Fog counts the share of complex (3+ syllable) words; Flesch–Kincaid uses the average syllables across all words. Fog tends to score jargon-heavy text more harshly.

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