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Free Readability Score Calculator (Flesch, Fog, SMOG & Grade Level)
Paste your copy and see every major readability index at once, plus the exact sentences and words dragging your score down — recalculated live, in your browser.
Why use this instead of doing it manually
Free readability score calculator: check any text against six formulas including Flesch Reading Ease, Flesch-Kincaid grade, Gunning Fog, SMOG and ARI, with the longest sentences and complex words flagged. Instant and private.
| Capability | The manual way | With ContentSERP |
|---|---|---|
| Formulas | One score in a word processor | Six indices side by side (FRE, FK, Fog, SMOG, CLI, ARI) |
| Actionability | A bare number | The longest sentences and hardest words listed |
| Privacy | Paste into a cloud editor | Scored on-device, nothing uploaded |
| Cost | Paid writing suites | Free, runs in your browser |
Frequently asked questions
What is a good readability score for SEO?
Aim for a Flesch Reading Ease around 60-70, roughly a 7th-8th grade level. Easier-to-read content is more likely to be quoted in featured snippets and AI answers, though readability is not a direct ranking factor.
Why do the formulas disagree?
Each weights sentence length and word complexity differently and some use syllables while others use letters. Treat the set as a range and focus on the flagged long sentences and complex words.
Does it work for languages other than English?
The syllable heuristic and formulas are calibrated for English. Results for other languages are indicative only.
Is my text uploaded anywhere?
No. Tokenising, syllable counting and scoring all run locally in your browser, so your draft stays private.
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