AI Readability Checker
Find difficult sentences and get suggestions for your audience. English readability estimates provide supporting context. Scores use estimated syllable counts. SMOG needs at least 30 sentences; other languages can use clarity review only. Try the same tool available in your dashboard, then carry your input, options and result into your account.
Find difficult sentences and get suggestions for your audience. English readability estimates provide supporting context.
Add at least 40 words to your text.
Estimated reading levels, quoted examples and specific ways to improve clarity.
What each readability score actually counts.
Four formulas, two inputs between them. Knowing which is which tells you when to use each.
- Flesch Reading Ease — 0 to 100, higher is easierThe best known, devised by Rudolf Flesch in the 1940s. It weighs average sentence length against average syllables per word and returns a score where 100 is easiest. Roughly 70–80 corresponds to a school grade 8 reading level, which is the usual target for writing meant for a general audience. Below 30 is heavy going for almost anyone.
- Flesch Kincaid Grade Level — a US school yearThe same two inputs arranged to output a grade instead of a score, which is why it is the one written into procurement rules and plain-language policies. A result of 9.0 suggests a US grade-nine reading level; it does not establish whether a particular reader will understand the text. It is the most widely used English readability formula, and it is measuring exactly what Reading Ease measures.
- Gunning Fog — sentence length plus complex wordsCounts words of three or more syllables rather than averaging syllables across everything, which makes it harsher on technical vocabulary specifically. Useful when the question is whether your terminology is the obstacle rather than your sentences.
- SMOG — built for health informationDeveloped for material where being misunderstood has consequences, and still standard in healthcare communication. It tends to return a higher grade level than Flesch Kincaid on the same text, which is deliberate: it was designed to be conservative where the stakes justify it.
- The raw counts underneath all of themAverage sentence length, longest sentence, percentage of long words, paragraph length. These are more actionable than any composite, because a score tells you there is a problem and a list of your three longest sentences tells you where it is.
Why a good readability score does not mean clear writing.
Worth understanding before you treat a number as a target, because the gap between what these formulas measure and what readability means is larger than it looks.
They count two things and nothing else. Sentence length and syllables. Not whether a sentence is ambiguous, not whether the argument follows, not whether the reader knows the vocabulary. Flesch designed these in the 1940s as a proxy, and a proxy is what they remain.
Which means any score can be improved without improving anything. Chop sentences at their commas. Replace precise long words with vague short ones. The score rises and the writing gets worse, and there is nothing in the formula that can tell the difference. Whenever a readability number becomes a target somebody has to hit, this is what happens to the prose.
Fragments beat paragraphs. The clearest demonstration is what bulleted text does to a score: six sentence fragments produce a very short average sentence length and a high Reading Ease, while a well-built paragraph that genuinely explains something scores worse. The formula is rewarding the absence of connective structure.
And precision is penalised. Technical and legal writing scores badly because domain vocabulary is polysyllabic and careful sentences carry qualifying clauses. If your readers know the terms, a high grade level is the right answer, and editing it down removes the precision they came for.
So use the score as a diagnostic rather than a goal. The genuinely useful output is not the composite number, it is the list of your three longest sentences — because those you can go and look at.
What to aim for, by who is reading.
There is no universally good score, only a score that fits an audience. These are the conventional targets and the reasoning behind each.
General public: grade 8, or Reading Ease 60–70. This is where news writing sits and where most plain-language requirements land. It is not a claim that adults read at grade 8; it is a recognition that people read distractedly and the easier text wins their attention.
Health, safety and legal notices: grade 6–8, checked with SMOG. Where misunderstanding has consequences, the conservative formula is the appropriate one. SMOG returns higher grade levels than Flesch Kincaid on the same text, and that caution is the point of it.
Business and marketing writing: grade 9–11. High enough to sound considered, low enough to be scanned. Most corporate prose sits well above this and reads as evasive rather than as expert.
Technical and academic writing: whatever the subject requires. The correct target here is not a number. Compare your document against others in the field rather than against a general standard, and treat a spike in your own longest sentences as the signal rather than the composite.
How ChatGPT, Claude, Gemini, DeepSeek, Grok, LLaMA and Perplexity text scores.
Two of these score misleadingly well and one scores misleadingly badly, which makes the model worth knowing before you read the number.
ChatGPT readability checker
Scores in a narrow band and stays there, which is itself informative.
ChatGPT output typically lands around grade 10 to 12 whatever you asked for, because it settles on a middle sentence length and holds it. The consequence for a readability check is that the average looks acceptable while the variance is almost nil — and variance is what makes prose comfortable to read.
Ask it for simpler writing and it shortens sentences without simplifying vocabulary, which moves the score more than it moves the reader. Check the long-word percentage separately.
Claude readability checker
The lowest readability scores of the major assistants, for a specific structural reason.
Claude writes longer sentences with more subordinate clauses, so both Flesch measures penalise it heavily. The prose is often genuinely clear despite that, which is the clearest demonstration on this page that the formulas measure length rather than comprehensibility.
If you need a Claude draft to hit a grade target, splitting sentences does most of the work. That is a real edit rather than a trick, because the clauses it stacks usually are separable.
Gemini readability checker
Scores well for reasons that have nothing to do with being readable.
Its bulleted output produces very short average sentence lengths, so Flesch Reading Ease comes back high on text that is fragmented rather than clear. This is the formula's biggest blind spot and Gemini triggers it constantly: a list of six sentence fragments scores better than a well-built paragraph.
Convert the bullets to prose before checking, otherwise the number describes the formatting rather than the writing.
DeepSeek readability checker
The hardest scores of any assistant, and usually accurately so.
Its technical register produces long words and long sentences together, which is the combination every formula punishes. Gunning Fog in particular will spike, because it counts three-syllable words directly.
Here the low score is generally telling the truth. DeepSeek drafts genuinely are dense for a general audience, and the fix is vocabulary rather than punctuation.
Grok readability checker
The best raw scores and the least consistent ones.
Its conversational register uses short words and short sentences, so Flesch Reading Ease comes back high. That is a genuine readability advantage rather than a formatting artefact, which makes it the exception among the assistants.
What varies is register rather than complexity. A Grok draft can be easy to read and wrong for the context, and no readability formula measures appropriateness.
LLaMA readability checker
The widest spread of scores within a single document.
LLaMA is weights rather than a product, so output depends on the deployment. In practice a document can shift grade level substantially between sections, which is unusual and visible if you check by section rather than as a whole.
That internal variance is worth more than the average. A document whose readability swings between sections reads as assembled rather than written.
Perplexity readability checker
Citation-shaped sentences score badly for a structural reason.
Sentences built to hold a bracket carry extra subordinate clauses, so grade level runs high. Stripping the citation markers leaves the clause structure behind, which means the readability cost survives the thing that caused it.
Rebuilding those sentences without the attribution scaffolding usually drops a grade level or two and reads better regardless of the number.
Readability checker questions.
What is a good readability score?
For general audiences, Flesch Reading Ease of 60–70 or a Flesch Kincaid grade level of 8–9. News writing typically sits near grade 8, and plain-language requirements in government and healthcare often specify grade 8 or lower. For a specialist technical audience, a higher grade level is appropriate and forcing it down makes the writing worse.
What is the difference between Flesch Reading Ease and Flesch Kincaid?
They use the same two inputs — average sentence length and average syllables per word — arranged to produce different outputs. Reading Ease gives a 0–100 score where higher is easier. Flesch Kincaid gives a US school grade level where higher is harder. If you have one you effectively have the other.
Can readability scores be gamed?
Easily, and this is the most useful thing to know about them. Both Flesch formulas count only sentence length and syllables, so you can improve any score by chopping sentences at commas and swapping long words for short vague ones. The result reads worse and scores better. If a number is a target rather than a diagnostic, that is what people will do to it.
Does a good score mean my writing is clear?
No, and the gap is worth understanding. The formulas cannot see whether a sentence is ambiguous, whether the argument follows, or whether the vocabulary is right for the reader. A list of disconnected fragments scores well. A precise technical sentence scores badly. Use the score to find your longest sentences, not to certify your prose.
Why does my technical writing score badly?
Because domain vocabulary is polysyllabic and precise sentences carry qualifying clauses. Gunning Fog penalises this hardest since it counts three-syllable words directly. If your audience knows the terms, a high grade level is the correct outcome and not a defect to be edited away.
Can it check readability of ChatGPT, Claude and Gemini text?
Yes, and the sections above cover how each behaves. Worth knowing that Gemini's bulleted output scores misleadingly well because fragments produce short average sentences, and Claude scores misleadingly badly because its long clear sentences are still long.
Which formula should I use?
Flesch Kincaid grade level for general work, because it is what most policies and clients specify. Gunning Fog when you suspect vocabulary rather than sentence length is the obstacle. SMOG for health or safety material, where it is standard and deliberately conservative.
Does readability affect SEO?
Not directly as a ranking factor, and indirectly through behaviour: text people can read gets read. The useful version of this is that writing for your actual audience serves both, and writing to hit a number serves neither.
Should I always aim for grade 8?
Only if your audience is general. Grade 8 is the right target for public-facing information and the wrong one for a specialist document, where forcing simplification strips the precision your readers need. The question is always who is reading, not what the number says.
Is my text stored?
The document is attached to your account so you can return to it, and you can delete it whenever you like. It is not used to train anything.