Readability Score — Flesch, Flesch-Kincaid, Fog, SMOG & More
Six standard formulas, one honest verdict on how hard your text is to read — and what to fix first.
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Grade-level formulas
| Flesch–Kincaid grade | — |
| Gunning Fog index | — |
| SMOG index | — |
| Coleman–Liau index | — |
| Automated Readability Index | — |
US school grade needed to read the text comfortably. 8 ≈ age 13–14; 12 ≈ high-school senior; 16 ≈ college graduate.
Text statistics
| Sentences | — |
| Words | — |
| Syllables | — |
| Words per sentence | — |
| Syllables per word | — |
| Complex words (3+ syllables) | — |
| Long sentences (25+ words) | — |
| Reading time (≈ 240 wpm) | — |
What would help most
Check how readable your writing is with the six standard formulas — Flesch Reading Ease, Flesch–Kincaid Grade, Gunning Fog, SMOG, Coleman–Liau and the Automated Readability Index — plus the sentence and syllable statistics they are built from. A consensus grade level summarises them, and a short list tells you which lever (sentence length or word length) would move the score most.
Paste anything from a paragraph to a whole article. Nothing is uploaded.
How to use Readability Score Checker
- Paste your text. Three or more sentences give a reliable score; a single line is noise.
- Read the Flesch score (0–100, higher is easier) and the consensus grade.
- Check the suggestions — long sentences and three-syllable words are the two things every formula punishes.
- Edit and re-paste. Most web copy should land around 60–70 (plain English, grade 8–9).
What the formulas actually measure
All six are regressions over two variables: average sentence length and average word length (in syllables or letters). Nothing else. They were calibrated in the mid-20th century against school reading tests, and they work because those two variables really do predict how hard prose is to process. What they cannot see: jargon made of short words, ambiguous sentences, bad structure, or whether the content is nonsense. A readability score is a speed limit sign, not a review.
The formulas at a glance
- Flesch Reading Ease — the classic 0–100 scale. 60–70 is plain English; Time magazine scores about 52, the Harvard Law Review in the low 30s, and most insurance policies below 40.
- Flesch–Kincaid Grade — the same inputs mapped to a US school grade. The US military's standard for technical manuals.
- Gunning Fog — penalises "complex" words (3+ syllables). A Fog of 12 is high-school senior; 8 is ideal for general readers.
- SMOG — designed for health materials; tends to run 1–2 grades above the others because it targets full comprehension, not just "gets the gist".
- Coleman–Liau and ARI — use letters per word instead of syllables, so they are immune to syllable-counting quirks.
Because they weight the two inputs differently, they spread across a few grades on the same text. The consensus shown is the median, which ignores whichever formula is the outlier for your particular prose.
How to improve a score without dumbing down
Split sentences at "and", "which" and "however". Prefer the short word when it means the same thing (use, not utilise; help, not facilitate). Cut hedges. Put one idea per sentence. None of this simplifies the thinking — it removes friction between the thinking and the reader. Long technical terms that have no synonym are fine; the score will complain, and you can ignore it knowingly.
Syllable counting
English spelling makes syllable counting heuristic — silent e, "-ed", "-le" endings, diphthongs. The counter here handles the common cases and is within a few percent on ordinary prose, which is all the formulas were ever calibrated for. For word counts alone, see the word counter.
Frequently asked questions
What is a good readability score?
For general web copy, a Flesch Reading Ease of 60–70 (grade 8–9). Consumer-facing legal and health text is often required to reach 60+. Academic writing typically sits at 30–50 and that is fine for its audience; the point is matching the reader, not maximising the number.
Why do the formulas disagree by several grades?
They weight sentence length and word length differently, and SMOG in particular targets full comprehension, so it runs high. A two-to-three grade spread is normal. The consensus figure is the median — it ignores whichever formula is the outlier for your text.
Does a low score mean my writing is bad?
No — it means the surface is hard to process: long sentences, long words. That may be appropriate (a physics paper) or not (a privacy notice). The score cannot judge clarity of thought, only friction. Use it as a prompt to shorten, not as a grade.
How accurate is the syllable count?
Within a few percent on ordinary English prose. Silent e, -ed, -le and vowel pairs are handled; rare words and names may be off by one. Coleman–Liau and ARI use letter counts instead of syllables, so if syllables look off, those two are unaffected.
How much text do I need?
At least three sentences, ideally a hundred words or more. The formulas were designed for passages, and the SMOG formula in particular assumes 30 sentences; on very short text every score is noisy.