The Gunning Fog Index estimates the years of formal education a reader needs to understand your text on the first pass. It weighs two things: average sentence length and the share of complex words, meaning words of three or more syllables that are not proper nouns, common suffixes or compound joins. The formula is 0.4 times the sum of average words per sentence plus the percentage of complex words. A Fog score around 8 is ideal for a wide audience, professional writing often lands near 12, and technical or legal text can climb past 17. This calculator counts syllables with a dependable English heuristic and updates the score as you type. Everything runs locally in your browser, so your writing is analyzed privately and no text is ever sent to a server.
It estimates the reading grade needed for your text using average sentence length and the share of complex words with three or more syllables.
The Fog index counts words of three or more syllables as complex, excluding common suffixes and proper nouns.
A Fog index around 7 to 8 is easy to read, while scores above 12 suggest the text is dense and better suited to specialists.
The Gunning Fog Index estimates the years of formal education a reader needs to understand your text on the first pass. It weighs two things: average sentence length and the share of complex words, meaning words of three or more syllables that are not proper nouns, common suffixes or compound joins.
Yes. Gunning Fog Index Calculator is completely free, with no sign-up and no usage limits.
Yes. Gunning Fog Index Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Gunning Fog Index Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.