Readability Checker

What this tool does

Readability Checker calculates six established readability formulas for your English text and explains what the scores mean. It also lists the longest sentences and most frequent complex words, so you know exactly what to simplify.

Clear writing reaches more people. Government guidance, health leaflets and consumer contracts are often expected to be readable by someone with a secondary-school education, and web readers skim rather than study. Yet writers judge their own text as easier than it is, because they already know what it means.

This checker counts sentences, words, syllables and letters, then applies the published formulas. Flesch Reading Ease is 206.835 − 1.015 × (words per sentence) − 84.6 × (syllables per word), where higher means easier. Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index each estimate a US school grade, and the tool averages them. Syllables are estimated with a vowel-group rule tuned for English, so expect small differences from other calculators. Your text stays in the browser.

How to use Readability Checker

1. Paste at least a few sentences of English text, ideally 100 words or more, or click Sample.
2. Read the Flesch Reading Ease score and its description, then the average grade level.
3. Compare the individual grade formulas to see whether long sentences or long words drive the difficulty.
4. Set “Flag sentences with at least” a word count in Options, then review the Long sentences list.
5. Check “Most used complex words” for terms you could replace with shorter alternatives.
6. Edit your text in place and watch the scores update.

Tips for better results

• A Flesch Reading Ease of 60 to 70 corresponds to plain English that most adults read comfortably.
• Coleman-Liau and ARI count letters instead of syllables, so they react strongly to long words and less to long sentences.
• Splitting one 40-word sentence into two usually improves every score more than swapping individual words.
• Use SMOG for health information; it was designed by G. Harry McLaughlin in 1969 and is widely used for patient materials.

Common use cases

• Checking that a patient information leaflet suits a general audience.
• Editing a website’s help pages for readers skimming on a phone.
• Comparing the difficulty of two drafts of a cover letter or report summary.
• Making sure terms and conditions are understandable before publishing them.

Common mistakes to avoid

• Testing a single sentence or a bulleted list; formulas need running prose to produce stable numbers.
• Chasing a score by deleting technical terms readers actually need; define them instead.
• Applying the formulas to languages other than English, for which their constants were never calibrated.