Readability score
Seven English readability formulas in one pass — Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Coleman-Liau, ARI and Dale-Chall — with the score, the matching school grade, a difficulty level and advice on sentence length, long words, multi-syllable words and passive voice.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Text to score (English)
All seven formulas use the coefficients from their original papers. Syllables are estimated by rules, and Dale-Chall uses a built-in ~300 word familiar list instead of the original 3000 word list, so its score drifts.
Text metrics
Paste English text and it is scored immediately.
What this tool does
- Estimate the difficulty of English documentation or marketing copy: the grade levels from Flesch-Kincaid and Gunning Fog map onto a target reader.
- Edit for non-native readers — when the long-word and multi-syllable shares are high, swapping in shorter everyday words usually helps more than restructuring sentences.
- Review content or SEO: SMOG and Dale-Chall lean on rare-word density, which is handy for spotting jargon-heavy paragraphs.
- Teach rewriting: score a paragraph, rewrite it, and compare the seven numbers instead of relying on a gut feeling.
Example
Input
The cat sat on the mat.
Output
Flesch Reading Ease 116.15 (very easy) · Flesch-Kincaid Grade -1.45 (grade 0) · Gunning Fog 2.4 · SMOG 3.13 · Coleman-Liau -4.07 · ARI -5.09 · Dale-Chall 0.3 (grade 4)
All six words are short and single-syllable, so the grade formulas go negative — that is not an error, and the reported school grade is floored at 0.
Frequently asked questions
Why can Flesch Reading Ease exceed 100, or go negative?
Both formulas are linear fits, so extreme inputs produce values outside the usual range. A sentence of short single-syllable words pushes Reading Ease above 100, while a jargon-dense long sentence gives a negative grade. The raw score is kept for comparison and the reported school grade is floored at 0.
Why do the formulas disagree with each other?
They use different features: the Flesch family counts sentence length and syllables, Coleman-Liau and ARI count letters or characters, SMOG only counts multi-syllable words, and Dale-Chall looks at rare words. One paragraph can therefore differ by a grade or two between metrics — read the trend rather than trusting a single number.
Why is Dale-Chall higher than the others?
The original formula relies on a familiar-word list of about 3000 entries, which cannot be bundled in full here; a ~300 word high-frequency list stands in, and anything missing counts as difficult, so the percentage of difficult words — and the score — runs high (it reads as harder than it is). Use it as a relative measure.
How much text does SMOG need?
McLaughlin derived SMOG from 30 sentences, and the error grows noticeably with fewer. The tool still computes it, but below 100 words it adds a small-sample note so you know the number is a rough guide.
Can I score Chinese text with this?
Not directly. Every formula here is built on English word and syllable statistics, and Chinese has neither whitespace tokenisation nor the same syllable counting. When no English words are found the tool says so instead of inventing a number.
Keywords：readabilityFlesch Reading Ease可读性评分Gunning FogSMOG indexColeman-Liaureadability scoreFlesch-KincaidDale-Chall文本难度