SMOG 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

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Words

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Sentences

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Syllables

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Avg. words per sentence

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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.

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Result

This page opens the readability checker with the SMOG card highlighted — paste your text and the SMOG grade updates live as you type.

SMOG (Simple Measure of Gobbledygook) estimates the education level needed to fully understand a text: 1.043 × √(polysyllabic words × 30 ÷ sentences) + 3.1291. It is the standard formula for checking healthcare and patient-facing materials.

SMOG was designed for samples of 30 or more sentences, so scores on very short texts are approximate, and like the other formulas it is calibrated for English with heuristic syllable counting. The full tool shows all six classic scores side by side, computed entirely in your browser.

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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.