Readability Checker
Paste English text to estimate its Flesch Reading Ease score and four grade-level scores: Flesch–Kincaid, Gunning Fog, Coleman–Liau and ARI.
About the Readability Checker
Paste at least 10 words of English text and the checker works out five standard readability formulas as you type. The headline number is the Flesch Reading Ease score, where higher means easier and 60–69 is what Flesch called plain English. Below it, four grade-level formulas (Flesch–Kincaid, Gunning Fog, Coleman–Liau and the Automated Readability Index) estimate the US school grade a reader needs, and their average is shown with a band such as "High school, grades 9–12".
All five formulas measure two things: how long your sentences are and how long your words are. Flesch Reading Ease is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words), and the Flesch–Kincaid grade is 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59. Gunning Fog counts words of three or more syllables, while Coleman–Liau and ARI count letters instead of syllables. Syllables are estimated from spelling (vowel groups, minus silent endings such as a final "e"), so treat every score as an estimate rather than a precise measurement.
Use it to check whether a help article, product page or letter suits its readers. Sentence length has a large, predictable effect: splitting one 28-word sentence into two 14-word sentences raises the Flesch score by about 14 points, all else being equal. Check overall length with the Word Counter, or listen to your draft with Text to Speech to hear where sentences run on.
How to use the Readability Checker
- 1
Paste your text
Paste or type at least 10 words into the box. The scores appear automatically and update as you edit.
- 2
Read the Flesch Reading Ease score
The large number and its label, from "Very easy" to "Very difficult", summarise the text. The marker on the bar shows where it sits between 0 and 100.
- 3
Compare the grade levels
The table lists the four grade-level formulas. If they disagree, check the statistics: words per sentence drives Flesch–Kincaid and Fog, while letters per word drives Coleman–Liau and ARI.
- 4
Edit and check again
Shorten long sentences or swap long words for shorter ones, and watch the scores change.
What it can do
Five formulas at once
Flesch Reading Ease, Flesch–Kincaid Grade, Gunning Fog, Coleman–Liau and the Automated Readability Index.
Flesch's own bands
The Reading Ease label follows Flesch's table: 90+ very easy, 80–89 easy, 70–79 fairly easy, 60–69 plain English, 50–59 fairly difficult, 30–49 difficult, below 30 very difficult.
Text statistics
Words, sentences, estimated syllables, average words per sentence, average syllables per word and reading time at 200 words per minute.
Average grade band
The four grade scores are averaged and placed in a band from elementary to college level.
Limitations
- Designed for English only. Syllables and letters are counted from the letters A to Z, so other languages give meaningless scores.
- Syllable counts are estimated from spelling, and words such as "created" or "idea" can be miscounted, which shifts the Flesch, Flesch–Kincaid and Fog scores.
- Sentences are detected by . ! or ? followed by a space. Abbreviations like "Dr." count as sentence endings, and bullet points without full stops run together into one long sentence.
- The formulas measure surface features only; they cannot tell whether your text is clear, accurate or well organised.
- Short samples give unstable scores. A few hundred words give a steadier picture.
Privacy
Your text is analysed by JavaScript in your browser and is never sent to FlexyPdf's servers.
Frequently asked questions
What is a good Flesch Reading Ease score?
It depends on the audience. Flesch described 60–69 as plain English, a common target for writing aimed at the general public. Specialist and academic writing often scores between 30 and 50, and very simple text for young readers can score above 90.
Why do the four grade levels disagree?
They weigh different things. Flesch–Kincaid uses average syllables per word, Gunning Fog uses the share of words with three or more syllables, and Coleman–Liau and ARI use letters per word. Text with short sentences but long technical terms can score low on one and high on another, which is why the average is also shown.
Can the Flesch score go below 0 or above 100?
Yes. Very long sentences full of long words push it below 0, and very short, simple sentences push it above 100. The tool shows the real value and simply pins the marker to the end of the bar. Grade-level results below 0 have no meaning and are shown as 0.
Are the scores meaningful for Hindi or other non-English text?
No. These formulas were built and calibrated for English, and the syllable estimate only understands English spelling. Scores for other languages, even those written in the Latin alphabet, would not mean anything.
Why is my bulleted list scored as one huge sentence?
Sentence breaks are found by looking for . ! or ? followed by a space or the end of the text. Lines without that punctuation, such as bullet points and headings, are joined into one long sentence. Add full stops or check those parts separately.
Ratings & Reviews
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