Readability Checker
Flesch, Flesch-Kincaid, Fog and SMOG scores plus the sentences dragging them down. 100% free, no signup. Everything runs in your browser.
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This free readability checker scores your text with the five formulas people actually cite: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG and ARI. Around the scores it shows the working: average sentence length, syllables per word, a list of the complex words weighing the text down, your longest sentences flagged for attention, and an estimated reading time. A plain-English interpretation table translates the numbers, showing what range suits marketing copy versus technical documentation. Everything runs in your browser and your text is never uploaded.
I built this because I kept seeing readability scores quoted with no idea what to do about them. A Fog index of 16 is a diagnosis, not a treatment. So this checker always pairs the number with the evidence: the exact sentences running long and the exact words counted as complex. The part I got wrong first was presenting one score as the answer; five formulas disagreeing slightly turns out to be far more honest than one number pretending to be certain.
How to use
- Paste your text into the box: an article, email, landing page or documentation section.
- Read the five scores that appear as you type: Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG and ARI.
- Compare your numbers against the interpretation table to see whether they fit your audience and content type.
- Review the flagged longest sentences and the complex word list to see exactly what is driving the scores.
- Rewrite the worst offenders: split long sentences, swap complex words where a simpler one loses nothing.
- Paste the revision and watch the scores and reading time shift toward your target as you edit.
Why use our readability checker?
Five formulas beat one because they disagree in instructive ways. Flesch-Kincaid leans on sentence length, Gunning Fog and SMOG weight complex words heavily, ARI counts characters. When all five agree your text is dense, believe them; when they split, the detail below the scores tells you whether length or vocabulary is the culprit. A single blended score would bury exactly that insight.
The interpretation table turns scores into decisions. A Flesch Reading Ease of 55 is meaningless in isolation; knowing that 60 to 70 suits general marketing copy while technical documentation can sit lower gives you something to aim at. Guidance from the US government's plain language guidelines points the same direction: match the text to the reader, not to how smart the writer wants to sound.
The flagged sentences are where the tool pays for itself. Averages hide outliers, and one 70-word sentence can be the entire reason a paragraph loses people. Having your longest sentences pulled out and listed turns revision from rereading everything into a short queue of specific fixes.
The complex word list keeps you honest about jargon. Some long words are unavoidable in your field; plenty are habits. Seeing utilize, functionality and implementation stacked in a list makes it obvious which ones would survive contact with an editor.
It runs entirely in your browser, so drafts stay private and results are instant. There is no signup, no word limit and no upsell. Check one email or a whole guide, as many times as the revision takes.
Who is this tool for?
Marketers check landing pages and emails before they ship. Copy that scores at a comfortable reading level converts better for a broad audience, and the flagged sentences show exactly where a promising paragraph turns into a wall. I check my own tool pages here, and the first drafts are reliably worse than I expect.
Technical writers use the grade scores to calibrate documentation. Docs are allowed to be denser, but there is a difference between necessary precision and accidental fog, and the complex word list separates the two. Pair it with the seo content analyzer when a doc also needs to rank.
Teachers, students and anyone writing for a required reading level use the grade formulas directly. If the assignment or the audience calls for an eighth-grade level, the Flesch-Kincaid and SMOG numbers tell you where you stand, and the sentence flags tell you how to close the gap.
Health, finance and legal communicators have the strongest case of all: their readers are often stressed and skimming, and comprehension failures have consequences. Running patient letters or customer notices through the checker, then condensing the key points with the text summarizer, is a fast route to documents people actually understand.
Frequently asked questions
No. Every formula runs in your browser with JavaScript, and your text never leaves your machine. That makes the checker safe for unpublished drafts, internal communications and client work.
For general audiences, 60 to 70 reads comfortably. Marketing copy often aims for 60 or higher, news sits around 50 to 60, and technical or academic writing commonly falls below 50. The interpretation table on the page maps these ranges so you can pick a target that fits your reader.
Trust the consensus. Each formula measures slightly different things, so when all five point the same way the verdict is solid. When they diverge, use the detail: sentence-driven scores high means shorten sentences, word-driven scores high means simplify vocabulary.
The Fog and SMOG formulas count words of three or more syllables, with standard exceptions like compound words and common suffixes. The tool lists every word it counted so you can see the real culprits, and decide which are essential terms and which are just habit.
Not directly; Google does not use a readability formula as a ranking factor. Readable pages tend to hold visitors longer and earn more links, which does matter. I treat readability as a service to the reader first, with any search benefit as a side effect.
It is based on typical adult silent reading speed, around 220 to 250 words per minute, so treat it as a good median rather than a promise. Dense technical material reads slower; familiar topics read faster. For plain counts of words and characters, the word counter is one click away.
You can, but the formulas were designed for passages of 100 words or more, and scores on a single sentence swing wildly. For anything under a paragraph, read the syllables per word and sentence length directly instead of leaning on the composite scores.