How to use the readability checker
- Paste at least a few paragraphs of English text. Headings and list items count as sentences, so remove them if you only want to score the body text.
- Read the two scores at the top. The label under Reading Ease shows where it falls on Flesch’s scale.
- Look at words per sentence and syllables per word to see which of the two is pulling the score down, then edit and watch it change.
The formulas
Flesch Reading Ease
206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
Published by Rudolf Flesch in “A new readability yardstick” (Flesch, 1948). Scores normally fall between 0 and 100, but very simple text can score above 100 and very dense text below 0.
Flesch-Kincaid Grade Level
0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
Recalculated by J. Peter Kincaid and colleagues from reading tests of 531 Navy enlisted personnel (Kincaid et al., 1975), so the result reads as a grade level instead of a 0–100 score.
Words, sentences and syllables are counted with the same rules as the sentence counter and syllable counter. Because syllables are estimated by rule rather than looked up in a dictionary, the scores can differ slightly from other Flesch-Kincaid calculators.
Flesch reading ease score table
Flesch’s 1948 paper pairs each score range with a description and the school level of a typical reader:
| Score | Difficulty | Reading level |
|---|---|---|
| 90–100 | Very easy | 5th grade |
| 80–90 | Easy | 6th grade |
| 70–80 | Fairly easy | 7th grade |
| 60–70 | Standard | 8th and 9th grade |
| 50–60 | Fairly difficult | Some high school |
| 30–50 | Difficult | 13th to 16th grade (college) |
| Below 30 | Very confusing | College graduate |
Worked example
Readability formulas measure two things: how long your sentences are and how long your words are. Short words and short sentences raise the score.
- 24 words, 2 sentences, 35 syllables
- Words per sentence: 24 ÷ 2 = 12
- Syllables per word: 35 ÷ 24 = 1.458
- Flesch Reading Ease: 206.835 − 1.015 × 12 − 84.6 × 1.458 = 71.3, “fairly easy”
- Flesch-Kincaid Grade Level: 0.39 × 12 + 11.8 × 1.458 − 15.59 = 6.3, about sixth grade
Most of the difficulty comes from “readability” (5 syllables) and “formulas” (3); swap them for shorter words and the Flesch Kincaid score improves without touching sentence length.
How to improve your Flesch-Kincaid reading level
- Split long sentences. Every extra word per sentence costs about one point of Reading Ease and 0.39 of a grade.
- Prefer short words: “use” instead of “utilize”, “help” instead of “assistance”. Syllables per word has the larger coefficient: 0.1 more syllables per word costs about 8.5 points of Reading Ease.
- Keep technical terms when your readers need them. The score measures length, not meaning, so a precise long word can be the right choice.
What the Flesch Kincaid test does not measure
Both formulas only see sentence length and word length. They cannot tell whether ideas are in a logical order, whether jargon is explained, or whether the text is accurate, and they were built for English. Use the score as one check of reading level alongside reading your text aloud or testing it with real readers.