Gunning Fog index calculator
Under 12 for a wide audience; 8 or under for near-universal understanding. Gunning noted that popular magazines of his day wrote at around 10–12.
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Gunning Fog Index
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Formula: 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
- Words
- 0
- Sentences
- 1
- Words with 3+ syllables
- 0
How to read the Fog index score
| Score | Meaning |
|---|---|
| 5 or below | Very easy: understood by most 10–11 year olds |
| 6–8 | Plain English: the target for email, web copy and public information |
| 9–10 | Fairly difficult: fine for engaged professional readers |
| 11–12 | Difficult: typical of specialist reports |
| 13–16 | College level: academic and technical writing |
| 17+ | Graduate level: legal and scientific text |
Lower scores mean easier text.
Where the Gunning Fog Index comes from
Created by Robert Gunning, an American businessman, in his 1952 book The Technique of Clear Writing. “Complex words” are words of three or more syllables, excluding proper nouns, familiar compounds and common suffixes like -es, -ed and -ing.
Other readability formulas
- Flesch–Kincaid Grade Level: 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
- Flesch Reading Ease: 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
- SMOG Index: 1.043 × √(polysyllables × 30 ÷ sentences) + 3.1291
- Coleman–Liau Index: 0.0588 × L − 0.296 × S − 15.8 (L = letters per 100 words, S = sentences per 100 words)
- Automated Readability Index: 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43
Questions people ask
What is a good Gunning Fog score?
Below 12 is readable by a wide audience; below 8 is near-universal. A score of 17 or more is graduate level.
What counts as a complex word in the Fog index?
A word of three or more syllables. Gunning excluded proper nouns, combinations of easy words (like “bookkeeper”) and words that only reach three syllables because of -es, -ed or -ing. This calculator counts all 3+ syllable words, so it can read slightly higher than a hand count.
How do I reduce my Fog index?
Replace long words with short ones and split long sentences. The complex-word term is multiplied by 40, so cutting a few polysyllables per hundred words makes a big difference.