Reading Level Calculator

Score any block of English prose with six established readability formulas: Flesch Reading Ease, Flesch–Kincaid Grade Level, Gunning Fog, SMOG, Coleman–Liau, and ARI. The Flesch band gives a one-word verdict; the score grid shows every formula at once. Everything stays in this tab — nothing is uploaded.

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Scores
Flesch Reading Ease
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Higher = easier. 0–121.
Flesch–Kincaid Grade
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US grade level
Gunning Fog
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US grade level
SMOG Index
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US grade level · needs 10+ sentences
Coleman–Liau
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US grade level · no syllable count
ARI
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US grade level
Base counts
Metric Value
Characters—
Letters—
Words—
Syllables—
Complex words (3+ syllables)—
Sentences—

How the formulas work
  • Flesch Reading Ease — 206.835 − 1.015 × (words / sentences) − 84.6 × (syllables / words). Higher is easier. Bands: 90+ very easy, 80–89 easy, 70–79 fairly easy, 60–69 plain English, 50–59 fairly difficult, 30–49 difficult, <30 very difficult.
  • Flesch–Kincaid Grade Level — 0.39 × (words / sentences) + 11.8 × (syllables / words) − 15.59. The US grade the text would fit. Used by the US Navy, the US Army, and many plain-language guidelines.
  • Gunning Fog — 0.4 × ((words / sentences) + 100 × (complex words / words)). Counts words with 3+ syllables as complex. Originally designed for US journalism.
  • SMOG Index — 1.043 × √(complex words × (30 / sentences)) + 3.1291. McLaughlin's 1969 formula was calibrated against 30-sentence samples. We suppress the value for fewer than 10 sentences — the formula is misleading on short samples.
  • Coleman–Liau — 0.0588 × L − 0.296 × S − 15.8, where L = (letters / words) × 100 and S = (sentences / words) × 100. The only common formula that doesn't need syllable counting.
  • Automated Readability Index (ARI) — 4.71 × (characters / words) + 0.5 × (words / sentences) − 21.43. Designed for typewriter-era US Air Force technical manuals.
  • Syllable counting uses the standard English vowel-group heuristic with a small dictionary of known exceptions. It matches a human count within ±1 syllable on common prose.
  • Sentence counting splits on terminal punctuation (. ! ?) and collapses common abbreviations (Mr., Dr., U.S.) so they don't get miscounted.
  • Nothing leaves the browser. The whole tool runs on a small script and the text you paste never gets uploaded.