Readability Checker
Six readability formulas, each reported honestly with its own validity, an audience target instead of invented population claims, and the exact sentences driving your scores. Free, private, runs in your browser.
Analysis runs in your browser and your text is never uploaded. By default the draft lives in this tab only and disappears when you close it. Ticking the box stores it in this browser's local storage on this device; Clear wipes it. Avoid the box on shared computers if the text is sensitive.
Type or paste text to compare it against your target grade.
The bar is capped at 0 and 100 for display. The number above is the raw formula value and can leave that range.
Formulas disagree because they weigh sentence length, syllables and letters differently. That spread is real information, so no synthetic average is shown.
Syllables are an English estimate from a heuristic, not a pronunciation dictionary. Possible passive is a be-verb plus participle pattern with common adjectives filtered out; review each match, it is a pointer and not a verdict.
Sentences to review
Ranked by how much each sentence adds to your scores. Click a sentence to select it in the editor. Dismiss anything you disagree with; dismissals last until you clear or reload.
Nothing flagged yet. Long sentences, complex-word clusters and possible passive constructions will appear here.
The six readability formulas, explained
Every readability formula estimates the same thing from different inputs: how much schooling a reader needs to get through your text on a first pass. Each one weighs sentence length, syllables and letters differently, which is why this reading level checker reports all six separately with the assumptions attached, instead of blending them into a composite number that no formula author would recognize.
| Score | Formula inputs | Scale | Worth knowing |
|---|---|---|---|
| Flesch Reading Ease | Words per sentence, syllables per word | Higher is easier; raw values can leave 0 to 100 | Depends on syllable estimation |
| Flesch-Kincaid Grade | Words per sentence, syllables per word | US school grade | The primary metric on this page |
| Gunning Fog Index | Words per sentence, share of 3+ syllable words | Years of formal education | Counts every 3+ syllable word as complex, so name-heavy text reads high |
| SMOG Index | 3+ syllable words, scaled to 30 sentences | US school grade | Validated on 30-sentence samples; marked low confidence below that |
| Coleman-Liau Index | Letters per 100 words, sentences per 100 words | US school grade | No syllables at all, so it often disagrees with Flesch |
| Automated Readability Index | Characters per word, words per sentence | US school grade | Character based; short-word jargon can slip past it |
A worked example: "The quick brown fox jumps over the lazy dog." has 9 words, 1 sentence and 11 syllables. Flesch Reading Ease is 206.835 minus 1.015 times 9 minus 84.6 times 1.22, which is 94.3, and Flesch-Kincaid Grade is 0.39 times 9 plus 11.8 times 1.22 minus 15.59, which is 2.3. One sentence is far below any formula's validated sample size, and the tool will tell you exactly that.
What a formula score can and cannot tell you
Formulas measure surface difficulty: sentence length and word length. They cannot see jargon a specialist audience finds easy, familiar brand names that read as long words, confusing structure, or whether the argument makes sense. Public-health style guides are blunt about this: a good score does not prove people understand the text, and the only real test is trying it on actual readers. That is why this page compares your text against a target you choose and never converts a formula grade into a claim about what share of the population will understand you.
How this checker measures, exactly
- Sentences are split with the browser's language-aware segmenter, with abbreviation and decimal handling, and headings or list lines count as their own units.
- Syllables come from a deterministic English heuristic with an exception list. Acronyms, numbers and unusual tokens are flagged as estimated instead of silently counted as one syllable.
- Raw formula values are never altered; the Reading Ease gauge is capped for display but the raw number stays visible.
- Analysis caps at 300,000 characters, enforced before processing starts, so a huge paste cannot freeze the page.
- Non-English scripts are refused with a notice, because English formulas on non-English text produce confident nonsense.
Readability and SEO: the honest version
A readability score is not a direct ranking factor. Google has said repeatedly that it does not score pages on reading ease, so rewriting a page purely to nudge Flesch numbers will not move rankings by itself. What readability does move is everything downstream: whether visitors read past the first paragraph, scroll, click, convert, share and come back. Clear writing at the right grade level for your audience earns the engagement that content is supposed to produce.
The catch is measuring that engagement honestly. Raw pageviews cannot tell you whether anyone read the page, and bots inflate exactly the metrics you would check. DevDome Analytics separates real human visitors from bots on every metric, so you can see which articles people actually read and which ones only look popular.
Readability checker FAQ
What is a good readability score?
It depends on who you are writing for, which is why this checker asks for a target instead of judging against one universal number. Plain-language and health writing usually aims for grade 6 or below, general web content for grade 7 to 9, and B2B or technical material can run at grade 10 to 12 because that audience reads dense text for a living. Set the audience preset above and the result tells you where you stand against your own target.
How does the Flesch Reading Ease calculator work?
The formula is 206.835 minus 1.015 times the average words per sentence, minus 84.6 times the average syllables per word. Shorter sentences and shorter words push the score up. The published formula is not capped: very simple text can score above 100 and very dense text below 0, so this page shows the raw value and only caps the visual gauge.
What is the Flesch-Kincaid grade level?
It converts words per sentence and syllables per word into a US school grade. It was developed for the US Navy in 1975 to grade training manuals and is the most widely recognized grade formula, which is why this page uses it as the named primary metric instead of inventing a composite score.
Why is there no single average grade level?
Because averaging five formulas with different inputs, scales and validation histories produces a number that none of them stands behind. SMOG was validated on 30-sentence samples, Coleman-Liau ignores syllables entirely, and Fog counts every long word as complex. This page names Flesch-Kincaid as the primary metric and shows the full range across the other formulas, so the disagreement stays visible instead of being averaged away.
Why does my readability score differ from other tools?
Mostly syllable counting and sentence splitting. English syllables cannot be counted perfectly without a pronunciation dictionary, so every checker uses a heuristic and small rule differences shift Flesch results by a point or so. This page flags every word whose syllable count is a guess, such as acronyms and numbers, so you can see how much estimation went into your score.
How does the possible passive detection work?
It looks for a be-verb or get followed by a past participle, like "was written" or "got approved", and filters out common adjectives such as "was tired" or "was crowded" that older tools miscount as passive. Every match is shown with the exact phrase so you can judge it, and you can dismiss anything you disagree with. The percentage is labeled possible passive because a pattern match is evidence, not proof, and it never feeds into your grade scores.
Which languages does the readability checker support?
English. The formulas and the syllable rules behind them were built and validated for English, so text in a non-Latin script such as Cyrillic, Arabic or Chinese gets a clear notice instead of fake scores. Mixed-language text is analyzed with a visible limited-accuracy warning that states the detected share of non-Latin letters.
Is my text uploaded or stored anywhere?
Your text never leaves the browser: analysis runs entirely on your device. By default the draft lives only in the open tab and is gone when you close it. If you tick "Save draft on this device" it is kept in your browser's local storage until you clear it, and the Clear button wipes it. Nothing is sent to a server, to analytics or anywhere else.
More free tools: Reading Level Checker · Flesch Reading Ease · Flesch-Kincaid Calculator · Word Counter · SERP Snippet Preview