Gunning Fog Index Calculator
Paste text to get its Gunning Fog index, an estimate of the US grade level needed to read it on a first pass. You also see how many words count as complex.
How to calculate the Gunning Fog index
- Paste or type your text into the box.
- Read the fog index and the reading band it maps to.
- Review the complex-word count, then simplify and retest.
Examples
Score a dense sentence
The committee deliberated on the complicated regulation.
Fog index about 19.9 (Very Difficult)
Frequently asked questions
How is the Gunning Fog index calculated?
The formula is 0.4 times the sum of words per sentence and 100 times the share of complex words. The result is a US grade level.
What is a complex word?
In Gunning Fog a complex word has three or more syllables. This tool decides that with a vowel-group syllable heuristic applied to each word.
How are syllables estimated?
Each word is lowercased, groups of consecutive vowels (a, e, i, o, u, y) are counted, a silent trailing e is dropped, and every word is at least one syllable.
Is the index always exact?
No. The complex-word count relies on a syllable estimate, so unusual words may be misclassified. Treat the index as a close approximation.
Is my text private?
Yes. The score is computed in your browser and nothing is uploaded or stored.
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