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Readability Score Checker

Score any English passage on six published readability formulas at once and see the word, sentence and syllable counts each score was built from.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Paste the English passage you want to score into the text box.
  2. 2.Select Analyze to compute all six formulas at once.
  3. 3.Read the Flesch Reading Ease band first, then compare the grade-level scores and check the raw counts underneath.

About Readability Score Checker

Readability Score Checker measures how hard an English passage is to read and shows the arithmetic behind the answer. Paste your text and the page returns six published readability scores at once, together with the raw counts every formula is built from: words, sentences, syllables, letters, characters, three-syllable complex words and polysyllables. Seeing the counts matters, because readability scores are simple functions of those counts, and two tools that disagree almost always disagree about counting rather than about the formula.

Six formulas are reported. Flesch Reading Ease returns a 0 to 100 style score where higher is easier, and comes with an interpretation band so the number means something. Those band labels follow the plain-language convention published by the US-funded MSKTC, not Flesch's own wording, and the bands are applied as open-ended thresholds because the score is genuinely unbounded: it can exceed 100 and it can go below zero. Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index all return a United States school grade level. They disagree with one another by design: Flesch-Kincaid and SMOG weigh syllables, Gunning Fog weighs long words per sentence, and Coleman-Liau and the Automated Readability Index count characters instead of syllables, which makes them useful as a cross-check when a syllable estimate looks suspect. Reading the six together is far more informative than trusting any single one. Coleman-Liau and the Automated Readability Index can legitimately return a negative grade on very short, very simple sentences; that is the published arithmetic rather than an error.

Every constant used here was checked against a primary or authoritative source rather than copied from a blog, and those sources are listed on this page. The Flesch-Kincaid and Automated Readability Index coefficients come from the 1975 Navy technical report that derived them; the SMOG constants come from McLaughlin's original 1969 paper; the Flesch Reading Ease coefficients and its interpretation bands come from a government plain-language document. Where published tables contradict each other, the disagreement was resolved with two independent sources rather than a majority vote of search results: the Flesch coefficient is 84.6 and not the 83.6 an OCR scan appears to show, and the Coleman-Liau coefficient is 0.0588 and not the 0.0855 that circulates in at least one journal table. One scope caveat is surfaced on the page rather than buried: McLaughlin defined SMOG for a sample of exactly thirty sentences, so below that the score is an extrapolation and the page says so while still showing it.

One part of the calculation cannot be exact, and the tool says so rather than hiding it. English has no authoritative algorithm for counting syllables from spelling, so the syllable count here is a rule-based estimate: it splits hyphenated words, handles consonant plus le endings, decides whether a final es or ed adds a syllable, drops silent final e and counts the remaining vowel groups, with a floor of one syllable per word. It is tested against a list of hand-checked words and it is right on ordinary prose, but it under-counts some vowel-adjacent words. Sentence detection is likewise heuristic: decimals, initials and a short abbreviation list are shielded so that a price or a title does not end a sentence early. Because grade-level formulas were validated on running prose, results on lists, code, tables or heavily numeric text should be treated as indicative only.

Everything is computed in your browser, so the text is never uploaded, stored or attached to an account, which matters for unpublished drafts and client material. Use the scores as a direction, not a verdict: they are good at telling you that a paragraph got denser after an edit, and poor at telling you whether a specific reader will understand it.

Methodology & sources

Count words, sentences, syllables, letters, characters, complex words and polysyllables from the pasted text with documented deterministic rules, then evaluate six published readability formulas whose constants were verified against primary sources, and report both the scores and the counts they came from.

Frequently asked questions

Why do the six scores disagree with each other?
They weigh different signals. Flesch-Kincaid and SMOG use syllables, Gunning Fog uses long words per sentence, and Coleman-Liau and ARI use characters. Reading them together is more reliable than trusting one.
How accurate is the syllable count?
It is a rule-based estimate. English has no authoritative spelling-to-syllable algorithm, so the counter is tested against hand-checked words and is reliable on ordinary prose but under-counts some words.
Why does the page warn me about SMOG on short text?
McLaughlin defined SMOG for a sample of exactly thirty sentences. Below that the score is extrapolated from a smaller sample, and because the formula takes a square root, the scaling also amplifies counting noise.

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