Free Readability Checker

How this tool computes its result

countSyllables is a heuristic: words of 3 characters or fewer count as 1 syllable; otherwise it strips a trailing "es"/"ed"/silent-e pattern and a leading "y", then counts groups of consecutive vowels (including y) via /[aeiouy]{1,2}/g. From total sentences (split on [.!?]+), total words (split on whitespace), and total syllables, it computes the Flesch Reading Ease score (206.835 − 1.015×avgWordsPerSentence − 84.6×avgSyllablesPerWord) and the separate Flesch-Kincaid Grade Level (0.39×avgWordsPerSentence + 11.8×avgSyllablesPerWord − 15.59), then buckets the Reading Ease score into six ease/grade labels from "Very Easy" (≥90) down to "Very Difficult" (<30).

Worked example

Text "The cat sat on the mat. It was a sunny day." has 2 sentences and 11 whitespace-split words (avg 5.5 words/sentence), and 12 counted syllables (avg ≈1.09 syllables/word) — mostly 1-syllable short words plus "sunny" counted as 2. Flesch Reading Ease ≈ 109.0, bucketed as "Very Easy" / "5th Grade". The separate Flesch-Kincaid Grade Level formula, however, computes to about -0.6 for this same short, simple text.

When not to use this tool

The Flesch-Kincaid Grade Level output is never clamped to a sane floor — as shown above, very short or simple text can legitimately compute a negative "grade level" (e.g. -0.6), which is not a meaningful reading-grade value; the tool displays it as-is. The syllable counter is also a regex heuristic, not a phonetic dictionary, so it will miscount syllables for irregular English words.

Common mistakes

• - Analyzing fewer than 5 sentences and treating the score as reliable — the tool itself flags this: "Add more content for a more accurate readability score" appears in the recommendations for short inputs.
• - Feeding in content with headings, bullet lists, or code blocks and expecting sentence splitting to handle them — the tool only splits on ".", "!", and "?", so unpunctuated list items get merged into the surrounding sentence count.
• - Applying the score to non-English content — the Flesch/Flesch-Kincaid constants (206.835, 84.6, 11.8, etc.) are calibrated for English and produce meaningless numbers on other languages.

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