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SMOG Index Calculator

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

Processed entirely in your browser — nothing you enter here is ever uploaded.

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Avg. words per sentence
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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

    About this tool

    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.

    Example. The cat sat on the mat. is counted as 6 words and 1 sentence, and Flesch Reading Ease is clamped to 100 because the raw score sits above the scale.

    Limit. Syllables are vowel groups plus a silent-e rule, so the six English formulas are not recalibrated for other languages.

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    Category overview

    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.