Readability Score Checker
Tighten your writing before you publish it.
What is the Readability Score Checker?
A readability score checker tells you how hard a piece of text is to read, using published formulas that count words, sentences and syllables rather than a subjective guess. This tool runs six of them at once — Flesch Reading Ease, Flesch–Kincaid Grade, Gunning Fog, SMOG, Coleman–Liau and the Automated Readability Index — on whatever you paste in, and updates as you type. Every score is plain arithmetic, not a model judgment: the same text always produces the same number, and you can see the exact calculation behind it. Writers, editors, teachers and UX copywriters use it to check that a blog post, a policy document or a set of instructions actually matches the reading level of the people who have to read it.
The tool also scores every sentence individually and shows them as a heat map, so instead of one number for a 2,000-word article you can see which specific sentences are easy, medium or hard. That matters more than the headline score, because one overloaded 45-word sentence can drag down an otherwise clear page, and the fix is to edit that sentence, not to rewrite the whole piece. Because the six formulas weight sentence length and syllable count differently, they will not always agree exactly — reading them together gives a more honest picture than trusting any single score.
Why use a free readability score checker?
Six published formulas, not one
Flesch Reading Ease, Flesch–Kincaid Grade, Gunning Fog, SMOG, Coleman–Liau and the Automated Readability Index all run on the same text, so you are not relying on a single metric that might be skewed by one unusual sentence.
Sentence-by-sentence heat map
Every sentence is scored individually and color-coded easy, medium or hard, so you can find and fix the specific sentences dragging your average down instead of guessing.
Updates as you type
Scores recalculate live while you edit, so you can watch the numbers move as you shorten a sentence or swap out a long word.
The formula math is shown, not hidden
Each score is displayed next to the exact expression and the word, sentence and syllable counts used to compute it — you can check the arithmetic yourself.
Nothing uploaded
All counting and scoring happens in your browser. The text you paste is never sent to a server.
How do you use the Readability Score Checker?
- 1
Paste your text
Drop in an article, email, policy document or landing page. There is no minimum length, but formulas that lean on sentence counts (like SMOG) get more reliable with at least a few sentences.
- 2
Read the six scores
Flesch Reading Ease is shown first because it is the most widely cited; the other five are grade-level estimates, so a result of "8" roughly means an eighth-grader could follow it.
- 3
Check the formula behind each number
Every score is shown with its exact expression and the underlying word, sentence, syllable and complex-word counts, so you can see exactly why the number came out where it did.
- 4
Use the heat map to fix specific sentences
Sentences marked "hard" (Flesch Reading Ease below 50) are the ones worth splitting, shortening or simplifying first — fixing three sentences often moves the whole-document score more than a general rewrite.
How is readability score checker calculated?
Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)Where:
- words
- Total word count of the text
- sentences
- Total sentence count, split on ".", "!" and "?"
- syllables
- Total syllable count, estimated per word by a vowel-group heuristic, not a dictionary lookup
The simple version
Longer sentences and longer words both pull the score down. The formula starts at 206.835 and subtracts a penalty for average sentence length, plus a bigger penalty for average syllables per word. A higher score means easier to read; 100 is about as easy as English gets, and the score is capped at that ceiling.
What does it look like in practice?
A dense, longer-word paragraph
Input
"The quick brown fox jumps over the lazy dog. It barked loudly at the mailman. Loud, sudden noises often startle nervous animals unexpectedly." — 23 words, 3 sentences, 38 syllables
Result
Flesch Reading Ease 59.3 (fairly difficult) · Flesch–Kincaid Grade 6.9 · Gunning Fog 8.3 · SMOG 8.8
Average sentence length is 7.7 words and average syllables per word is 1.65. The last sentence alone ("startle", "animals", "unexpectedly") supplies most of the complex-word penalty in Gunning Fog and SMOG.
A short, plain-English pair of sentences
Input
"The dog ran fast. It barked loudly at the mailman." — 10 words, 2 sentences, 12 syllables
Result
Flesch Reading Ease 100.0 (very easy) · Flesch–Kincaid Grade 0.0
Short sentences of mostly one-syllable words push Flesch Reading Ease above 100, so the score is capped there — this is the ceiling almost any plain English hits.
How accurate is it?
All six scores are computed directly from counts inside your own text — words, sentences, syllables and letters — using the published formulas below. There is no external dictionary, language model or reference corpus involved, so the same input always produces the same output.
- Flesch–Kincaid Grade = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
- Gunning Fog = 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)], where a complex word has 3 or more syllables
- SMOG Index = 1.043 × √(complex words × 30 ÷ sentences) + 3.1291
- Coleman–Liau Index = 0.0588 × L − 0.296 × S − 15.8, where L is letters per 100 words and S is sentences per 100 words
- Automated Readability Index = 4.71 × (letters ÷ words) + 0.5 × (words ÷ sentences) − 21.43
- Syllables are estimated with a vowel-group heuristic (roughly: count groups of adjacent vowels, adjust for silent "e" and "-le" endings), not a dictionary lookup — it is close for the vast majority of English words but can miscount unusual compounds or proper nouns.
- The formulas were built for standard English prose. They read numbers, code, bullet fragments and non-English text as ordinary words, which will distort the result for those content types.
What should you know before using it?
Flesch Reading Ease score bands, and the reading level and audience each one roughly corresponds to:
| Flesch Reading Ease | Reading level & typical audience |
|---|---|
| 90 – 100 | Very easy — 5th grade. Simple instructions, children's content. |
| 80 – 89 | Easy — 6th grade, conversational English. Social captions, SMS-style copy. |
| 70 – 79 | Fairly easy — 7th grade. Consumer blog posts, marketing emails. |
| 60 – 69 | Standard — 8th–9th grade. The commonly cited "sweet spot" for general web content. |
| 50 – 59 | Fairly difficult — 10th–12th grade. Trade publications, detailed how-to guides. |
| 30 – 49 | Difficult — college level. Industry reports, policy documents. |
| 0 – 29 | Very difficult — graduate level. Legal contracts, academic papers, scientific writing. |
Which tools relate to the readability score checker?
The readability score checker is one of 12 writing tools on this site. These are the ones most often used alongside it — either because they handle the next step in the same job, or because they answer a question this tool raises.
Sentence Checker
Flags the exact sentences that are too long, too short or overloaded with clauses — the same sentence-length issue that drives most of the Flesch and Fog penalties here.
Keyword Density Checker
High keyword density often forces awkward, repetitive phrasing that also tanks readability — worth checking both before you publish.
Text Summarizer
If a document scores as difficult, an extractive summary can show you which sentences carry the actual argument, separate from the sentences adding complexity without adding meaning.
Word Counter
Readability formulas are all ratios of counts — word count, sentence count, syllable count. Check the raw counts behind the score here.
When should you use a readability score checker?
Because the readability score checker runs entirely in your browser, it suits work you would not want to hand to a third-party server — client files, unpublished drafts, anything under an NDA. These are the situations people reach for it in most often.
Pre-publish content review
Check a blog post or landing page against a target grade level — many style guides for general web content aim for a Flesch–Kincaid Grade around 7–9.
Plain-language compliance
Government forms, insurance documents and healthcare materials are often required to hit a specific reading grade level. Run the text and check the Flesch–Kincaid or Coleman–Liau result against the target.
Education and ESL materials
Teachers use SMOG and Flesch–Kincaid to match reading passages to a specific grade level or a learner's current proficiency.
UX and forms writing
Error messages, tooltips and onboarding copy read by a broad audience benefit from staying in the "standard" or "easy" bands — the heat map shows exactly which lines to simplify.
Frequently asked questions
What is a good Flesch Reading Ease score for a website?
How is the readability score calculated?
Why do the six scores disagree with each other?
Is Flesch–Kincaid Grade the same as a US school grade level?
Does the tool use AI to judge readability?
Can I trust these scores for legal or academic writing?
Is my text uploaded when I use this tool?
Is the readability score checker safe to use?
This tool runs entirely inside your browser. Your text, files and settings are processed on your own device and are never uploaded to our servers — there is nothing for us to store, log or leak. You can confirm it yourself: open your browser DevTools, switch to the Network tab, and use the tool. You will not see an upload request. It also means the tool keeps working if your connection drops mid-task.
Where do these figures come from?
Every method, threshold and standard this page relies on, with a link to the document that defines it. Check them — a tool that will not show its sources is asking you to take its word for it.
- 1Derivation of New Readability Formulas (Automated Readability Index, Fog Count and Flesch Reading Ease Formula) for Navy Enlisted Personnel
Kincaid JP, Fishburne RP, Rogers RL, Chissom BS — Naval Air Station Memphis, Research Branch Report 8-75 · 1975
Supports: The Flesch–Kincaid Grade Level formula and the Automated Readability Index formula used on this page, and the recalculation of the Flesch Reading Ease constants.
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