Readability Checker: Grade Level and Reading Ease for Any English Text
Paste English copy and get Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, and ARI scores plus word and syllable stats — all in the browser.
Table of Contents
A paragraph can be factually correct and still fail. Long sentences, stacked clauses, and three-syllable nouns push a page out of reach for the people you meant to help. Editors feel that drag. Formulas measure it.
The free Readability Checker scores English text with six classic indexes: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau, and the Automated Readability Index. It also reports words, sentences, syllables, complex words, and averages. Everything runs in your browser. Nothing is uploaded.
Use it on help articles, product copy, research summaries, classroom passages, or legal notices you want a non-lawyer to finish. This guide explains what each score means, how the tool counts syllables and complex words, and how to rewrite toward a target grade without flattening your voice.
Why Use a Readability Checker?
- Six formulas, one paste. A single index can mislead. Averaging Flesch-Kincaid, Fog, SMOG, Coleman-Liau, and ARI shows whether the verdict is a fluke or a pattern.
- Private by default. Drafts, unpublished posts, and internal docs never leave the device. There is no account and no paste-bin.
- Actionable stats, not a black box. Word count, sentence count, syllables, and complex-word count sit next to the scores so you can see why the grade moved.
- Copy a full report. One click copies scores and statistics for a ticket, a review comment, or a style-guide checklist.
- Built for English heuristics. Syllable estimates and Fog’s “complex word” rules follow the conventions these formulas were designed around.
- Instant sample. Load sample text if you want to see the dashboard before pasting your own.
Key Features
| Feature | What it does | Why it matters |
|---|---|---|
| Flesch Reading Ease | 0–100 style score from sentence length and syllables per word | Quick “easy / standard / difficult” label for editors |
| Grade indexes | Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, ARI | Maps copy to a U.S. school-grade band |
| Average grade | Mean of the five grade formulas | One headline number for a brief or CMS field |
| Text stats | Words, sentences, syllables, complex words, averages | Shows the lever to pull: shorter sentences vs simpler words |
| Copy report | Plain-text dump of every score and count | Share results without screenshots |
| Client-side | Analysis stays in the tab | Safe for confidential drafts |
- Sentences are counted from runs of ., !, or ?. A fragment with no terminator undercounts sentences and inflates words-per-sentence.
- Complex words are English tokens with three or more syllables, excluding a small-word list and capitalized proper nouns — the usual Gunning Fog convention.
- Coleman-Liau and ARI use letter counts, not syllables, so they still move when you shorten words even if syllable estimates are noisy.
How to Use
- Open the Readability Checker.
- Paste English text, or click Sample to load a demo passage.
- Read the headline Grade (average of five indexes) and Flesch Reading Ease (Very Easy through Very Difficult).
- Scan the breakdown. If Fog and SMOG sit above Flesch-Kincaid, you likely have too many long words, not just long sentences.
- Rewrite, paste again, and copy the report when the band matches your audience. Clear the box when you are done.
Understanding the Scores
Readability formulas are regressions from the mid-20th century. They were trained on English school materials. They do not measure truth, tone, or whether a joke lands. They estimate how much schooling a typical native reader needed for similar sentence and word patterns.
Flesch Reading Ease is the odd one out: higher is easier. Roughly 90–100 is very easy, 60–70 is standard news-magazine range, 30–50 is college-ish, and below 30 is dense. The formula penalizes long sentences and high syllables per word.
Flesch-Kincaid Grade Level turns the same inputs into a U.S. grade. Many public-facing teams aim near grades 7–9. Medical and legal pages often sit higher; that is a choice, not a law.
Gunning Fog mixes words per sentence with the share of complex words (three-plus syllables). Cutting jargon drops Fog faster than trimming a comma splice.
SMOG (Simple Measure of Gobbledygook) scales complex words as if you had a 30-sentence sample. Short pastes are statistically thin; treat SMOG as a directional check, not a courtroom exhibit, until the passage is a few hundred words.
Coleman-Liau and ARI skip syllables. They use characters per word and words per sentence. They help when the syllable heuristic disagrees with your ear — for example on acronyms or hyphenated compounds.
The tool’s average grade is the mean of Flesch-Kincaid, Fog, SMOG, Coleman-Liau, and ARI. Flesch Reading Ease stays on its own 0–100 scale.
Syllables are estimated with a vowel-group heuristic: strip a silent trailing e, count vowel runs, keep at least one syllable. That is good enough for these formulas and matches how many desktop checkers behave. It is not a dictionary lookup, so “queue” and brand names can be off by one.
Practical Use Cases
Help centers and product copy
Support articles fail when every step is one 40-word sentence. Paste a draft, note average words per sentence, and split procedures into short commands. Aim for Flesch Ease in the 60s unless the audience is specialists who expect the jargon.
SEO and content briefs
Search teams still put “grade 8” in briefs. Paste the outline or the finished post. If keyword stuffing inflates word count without adding sentences, ARI and Coleman-Liau will climb. Pair this checker with a Word Counter when the brief also has a length target.
Classrooms and assessments
Teachers can check whether a passage matches the intended grade before assigning it. Students can paste their own essays to see whether Fog spiked from stacked academic nouns. The scores are English-oriented; they are a poor fit for Thai, code, or heavily formulaic math text.
Compliance and public notices
Agencies and insurers often need “plain language.” Run the notice, copy the report into the review thread, then rewrite the worst paragraphs. Formulas will not catch missing definitions, but they catch the sentence that nobody finishes.
Best Practices
- Paste a representative chunk. A hero headline plus a 12-word CTA will look easier than the 800-word body. Score the body, or score sections separately.
- End sentences with real punctuation. Lists without periods skew words-per-sentence.
- Do not chase a single index. If four grades agree and SMOG is an outlier on a 40-word blurb, trust the cluster.
- Cut long words before you cut meaning. Replacing “utilization” with “use” moves Fog and Flesch without deleting the point.
- Keep audience in mind. Grade 5 is not automatically better. Expert docs can sit at college level if the readers are experts.
- Re-score after edits. One long parenthetical can swing averages on a short paste.
Need a second pass on the same draft? Open the checker, paste, rewrite until the average grade matches the brief, then copy the report into the ticket. The Readability Checker stays local, so you can work through confidential copy without a third-party analyzer.
Related Tools You Might Like:
- Word Counter — words, characters, and reading-time style counts
- Text Statistics — deeper counts for letters, words, and structure
- Character Counter — tight limits for titles, bios, and meta fields
Happy writing — and keep the sentences short enough to finish.