Analyze text readability with Flesch Reading Ease, Flesch-Kincaid Grade Level, and Gunning Fog Index.
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The Readability Checker analyzes any text you paste in and reports how easy it is to read, using established formulas like the Flesch Reading Ease score and the Flesch-Kincaid Grade Level. It counts words, sentences, and syllables in real time and translates those counts into a 0-100 ease score and an approximate US school grade level, so you can see at a glance whether a passage reads like a children's book or a legal contract.
It is built for content writers, SEO teams, teachers, technical documentation authors, and anyone who needs prose that a broad audience can understand. Everything runs in your browser as you type, making it a quick way to test blog posts, marketing copy, product descriptions, or help-desk articles before you publish.
The Flesch Reading Ease score is calculated as 206.835 minus (1.015 times the average number of words per sentence) minus (84.6 times the average number of syllables per word). The result usually lands between 0 and 100: scores of 90-100 are very easy (roughly 5th grade), 60-70 are plain English suitable for most readers, and scores under 30 are best understood by university graduates or professionals.
The Flesch-Kincaid Grade Level uses the same two inputs but maps them onto US school grades with the formula (0.39 times average words per sentence) plus (11.8 times average syllables per word) minus 15.59. A result of 8.0 means an average American eighth-grader could understand the text. Both formulas reward shorter sentences and shorter, fewer-syllable words, which is why splitting a long sentence or replacing 'utilize' with 'use' will nudge your scores toward easier reading.
Because syllable counting relies on heuristics rather than a full pronunciation dictionary, scores for very technical text, acronyms, or unusual proper nouns should be treated as a close estimate rather than an exact reading age.
Yes, it is completely free with no sign-up required. All analysis happens locally in your browser, so your text is never uploaded to a server or stored anywhere.
For general web content and blog posts, aim for a score of 60-70, which corresponds to plain, conversational English around an 8th to 9th grade reading level. Higher scores are easier; scores below 50 read as difficult and are better suited to academic or professional audiences.
It estimates the US school grade needed to understand the text. A grade level of 7.0 means a typical seventh-grader could read it comfortably, while 12.0 corresponds to a high-school senior.
It uses a vowel-group heuristic that scans each word for clusters of vowels and adjusts for common silent endings, then estimates syllables from that. This is accurate for most everyday English words but may be slightly off for technical terms, brand names, or acronyms.
Both formulas depend heavily on average sentence length. Splitting a very long sentence into two shorter ones sharply lowers the average words per sentence, which can move the grade level down by a full grade or more.
The Flesch and Flesch-Kincaid formulas were designed and calibrated for English, so scores for other languages will not be meaningful even though the word and sentence counts still work.
There is no fixed limit for typical use. You can paste a full article or a long document, and the browser will analyze it, though extremely large inputs may respond more slowly on older devices.