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Flesch-Kincaid Readability Calculator

Measure your text's reading ease and grade level

How it is calculated

The tool counts words (W), sentences (S) and syllables (Y) in the text you paste. Then Reading Ease = 206.835 − 1.015 × (W / S) − 84.6 × (Y / W) and Grade Level = 0.39 × (W / S) + 11.8 × (Y / W) − 15.59.

How the counting works: a word is any space-separated piece that contains an English letter, so a token made only of digits is not counted. A sentence is each run of . ! ? characters (at least one sentence is assumed). Syllables are estimated by counting groups of consecutive vowels (a, e, i, o, u, y) and dropping one for a silent final e. This is built for English; other languages give unreliable scores. Scores can exceed 100 or go below zero for very simple or very dense text.

Worked example

Text: "The cat sat on the mat. It was a sunny day and the cat was happy." It has 16 words, 2 sentences and 18 syllables (sunny and happy count two each). Words per sentence: 16 / 2 = 8. Syllables per word: 18 / 16 = 1.125. Reading Ease = 206.835 − 8.12 − 95.175 = 103.54. Grade Level = 3.12 + 13.275 − 15.59 = 0.81, which is very easy text.

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Common mistakes

  • Testing a single short sentence or a few words; the averages are only meaningful over a paragraph or more.
  • Pasting text with decimals, abbreviations or web addresses; every full stop counts as a sentence end, so "3.14" or "e.g." splits sentences and lowers the average length.
  • Using the score for non-English text; the syllable estimate is based on English spelling, so Turkish or German passages are not rated correctly.
  • Leaving in headings, bullet lists or captions with no ending punctuation; they merge with the next sentence and inflate its length.
  • Treating a high Reading Ease as a quality mark; short words and short sentences make the score high even when the writing is vague, and the grade level is a US school-grade scale, not a measure of your readers' age.

About this calculator

This calculator runs your text through two related formulas: Rudolf Flesch’s 1948 Reading Ease score and the grade-level version J. Peter Kincaid adapted from it for the U.S. Navy in 1975. The Flesch Reading Ease score is 206.835 − 1.015×(words/sentences) − 84.6×(syllables/words), producing a 0–100 scale where higher means easier to read — 90+ is roughly 5th-grade prose, 30 or below is closer to dense academic or legal writing. The Flesch-Kincaid Grade Level converts the same sentence-length and syllable-density inputs into a U.S. school grade: 0.39×(words/sentences) + 11.8×(syllables/words) − 15.59.

Technical writers, UX copywriters, and journalists use these scores to keep instructions and articles accessible to a general audience, while Microsoft Word and Google Docs still ship the same formulas under "readability statistics." Government agencies and insurers in the U.S. often mandate a specific Flesch-Kincaid grade level for consumer-facing forms and plain-language disclosures.

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Comments (1)

  • Editorial team

    A whole-document score can hide a hard section, so paste one section at a time and compare. A negative grade level is possible for very plain text, and the grade is a U.S. school-grade scale, not your reader's age. The tool only reads English letters, and a token made purely of digits is skipped as a word. For a policy page or a set of instructions, which grade level would you want to see?

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