Readability Checker
Score your writing with Flesch Reading Ease, grade level and Gunning Fog — live as you type.
🔒 Runs entirely in your browser — nothing you type is uploaded or stored on a server.
The Readability Checker measures how easy your writing is to read, using the same formulas professional editors, teachers and plain-language reviewers rely on. Paste your text and it instantly computes your Flesch Reading Ease score, Flesch-Kincaid grade level and Gunning Fog index — three different, well-established readability formulas, all from one pass of the same text — along with the raw ingredients behind them: average words per sentence, syllables per word and the share of complex words. A plain-English verdict tells you who will find the text comfortable to read, from a 5th grader to a graduate student.
Also on Txtset: check total words and keyword density · measure character and tweet limits · identify the language of your text.
Flesch Reading Ease is the one most people mean when they search for a “Flesch test” or “Flesch reading test”, and it is the formula this tool leads with. Developed by Rudolf Flesch in 1948, it scores a 0–100 scale from two ingredients: how long your sentences are and how many syllables your words have. The exact equation, computed live as you type, is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words). Shorter sentences and shorter words push the score up; long, syllable-heavy sentences push it down. A higher score always means easier reading — there is no “good” fixed number, only a target for your audience.
Flesch-Kincaid Grade Level reuses the same two ingredients but reports them differently — not a 0–100 ease score, but the US school grade a reader needs to follow the text comfortably. The formula is 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ word) − 15.59. A result of 8.0 means a typical 8th grader can read it without strain; most newspapers and popular fiction sit around grade 7–9, and this tool reports the number to one decimal place so small edits show up immediately.
Gunning Fog is the third figure, and it measures something the other two don't: how many “complex” words — three syllables or more — your text leans on. Its formula is 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)], and like Flesch-Kincaid it reads out as a grade level. Because it weights long words so heavily, a text can score comfortably on Flesch Reading Ease and still show a high Fog index if it is full of multi-syllable jargon — the two formulas together catch different problems.
The score bands matter as much as the number. A Flesch Reading Ease of 90 or above reads like a children's comic (5th grade); 80–89 is easy, conversational English (6th grade); 70–79 is fairly easy (7th grade); 60–69 is the plain-English sweet spot most web content and journalism aims for (8th–9th grade); 50–59 is fairly difficult, high-school level; 30–49 is difficult, suited to college readers; and anything under 30 is dense, academic text that would benefit from shorter sentences and simpler words. The tool's verdict line names the band your text falls into as you edit.
These aren't academic curiosities — they have real consequences. Insurance policies, loan documents and other consumer contracts in many US states are legally required to clear a minimum Flesch score before they can be sold, because regulators decided readers deserve to actually understand what they're signing. Plain-language guidelines for government, healthcare and financial writing set similar targets, word processors have shipped a Flesch score in their proofing tools for decades, and teachers use grade-level formulas to check whether a handout or exam question is pitched at the right class. Checking a score before you publish takes seconds and answers the same question all of those readers are asking silently: is this easy enough to follow?
The scores update live as you edit, so you can watch all three numbers move as you shorten sentences and swap long words for short ones. Syllables are counted with a fast, well-tested heuristic rather than a dictionary lookup, so very unusual words can be off by one syllable — it doesn't change which band your text lands in. Everything is calculated in your browser; your draft is never uploaded. The tool works for anything from a tweet-length blurb to a full article, though all three formulas are most reliable with at least 50 words, since a single short sentence can swing the ratios wildly.
How to use
- Paste your draft into the box — at least a paragraph gives meaningful scores.
- Read the Flesch Reading Ease score: higher is easier, with 60–70 the plain-English sweet spot for general audiences.
- Check the Flesch-Kincaid grade level and Gunning Fog index — both estimate the school grade a reader needs, from two different angles.
- Look at words-per-sentence and complex words to see why a score is high or low.
- Edit the text and watch all three scores update live until you hit your target band.
Examples
A draft scoring 45 on Flesch Reading Ease (difficult) with 28 words per sentence tells you to split long sentences; a few edits later it reads 65 and the verdict says “plain English”.
Before sending a company-wide announcement, check it scores at least 60 on Flesch Reading Ease so everyone — not just specialists — reads it easily.
A teacher pastes a handout and sees a Flesch-Kincaid grade of 11.3 — too hard for a 7th-grade class — and simplifies vocabulary until it fits.
A paragraph scores a reasonable 62 on Flesch Reading Ease but a Gunning Fog of 15 — the Fog score flags the long technical terms that Flesch missed.