Gunning Fog Index Calculator

Score your text live with six classic readability formulas: Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and ARI.

Source Text

0

Words

0

Sentences

0

Syllables

0

Avg. words per sentence

0

Avg. letters per word

Flesch Reading Ease —

206.835 − 1.015 × (words/sentence) − 84.6 × (syllables/word)

Flesch-Kincaid Grade —

0.39 × (words/sentence) + 11.8 × (syllables/word) − 15.59

Gunning Fog Index —

0.4 × (words/sentence + 100 × complex words/words)

SMOG Index —

1.043 × √(polysyllables × 30/sentences) + 3.1291

Coleman-Liau Index —

0.0588 × L − 0.296 × S − 15.8 (L letters, S sentences per 100 words)

Automated Readability Index —

4.71 × (characters/word) + 0.5 × (words/sentence) − 21.43

Longest sentences

These formulas are calibrated for English; for other languages the scores are only indicative. Nothing is uploaded — the text is analyzed in your browser.

Processing... 0%

Result

This page opens the readability checker with the Gunning Fog card highlighted — paste your text and the fog index updates live with each change.

The Gunning Fog index estimates the years of formal education a reader needs: 0.4 × (average sentence length + 100 × complex words ÷ words), where complex words have three or more syllables. Business writing usually targets a fog index below 12.

This tool counts complex words with a syllable heuristic and skips the manual proper-noun exceptions of the original method, and the formula itself is English-calibrated — use the score as a comparative signal. Five more formulas are computed alongside it, all locally in your browser.

🛡️

Executed in Browser

Your files and inputs never leave this device. Processing runs completely offline. 100% Secure.

Accepted Formats & Rules

Live Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Coleman-Liau and ARI scores with the formula shown on each card.
Average sentence length, average word length and a list of your three longest, hardest sentences.
Heuristic syllable counting (vowel groups with silent-e handling) — no dictionary download, everything stays offline.

Key Benefits

✓ Complete privacy: the text is analyzed entirely in your browser and never uploaded anywhere.

✓ Six standard formulas at once, so you can compare scores instead of trusting a single number.

✓ Honest scoring: the formulas are calibrated for English, and the tool says so — for other languages the scores are indicative, not absolute.

Use Cases

• Check a landing page or help article before publishing so its Flesch-Kincaid grade lands in the 6-9 range a general audience can read comfortably.
• Compare two drafts of the same text and see which one lowers the reading level across all six formulas at once.
• Spot the three longest, hardest sentences on the page and rewrite them to bring the Gunning Fog and SMOG scores down.