Readability Checker: Flesch, SMOG & Gunning Fog Scores
Readability checker online: measure text readability with Flesch, SMOG, and Gunning Fog scores, grade levels, and improvement tips.
Updated 2026-08-26
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Features
- Five standard readability metrics in one pass: Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, and Coleman-Liau scores
- Grade level conversion for every metric: see roughly which school grade the text fits
- Score range interpretation: each score maps to a plain-language band from very easy to very confusing
- Long-sentence detection: sentences over 30 words are listed so you know exactly what to split
- Complex word list: every word with 3 or more syllables, sorted by difficulty, ready to replace
- Chinese text handled honestly: when CJK characters dominate, the English formulas are not forced on the text; word, sentence, and character stats plus long-sentence flags are still shown
- Real-time analysis: scores update as you type or paste, with no analyze button
- Text statistics: word, sentence, syllable, complex-word, and character counts at a glance
- Concrete improvement tips: split long sentences, replace complex words, shorten sentences for wider audiences
- Copy a plain-text report of every score and list in one click
How to Use
- 1Paste or type any English text into the input area; the five readability scores and statistics appear instantly.
- 2Read the score cards: Flesch Reading Ease gives an intuitive 0–100 ease score, the other four give US grade levels.
- 3Match the grade level to your audience: marketing copy for a broad audience usually sits below grade 8, technical documentation often above.
- 4Improve marketing or blog copy by targeting a Flesch Reading Ease score in the 60–80 band, the range most readers find comfortable.
- 5Check technical documentation difficulty before publishing: the Gunning Fog and SMOG grades show whether non-experts will struggle.
- 6Use the long-sentence list to find the sentences that hurt readability, then split each one into two or three shorter sentences.
- 7Scan the complex word list and replace jargon with everyday alternatives where the meaning survives.
- 8Use the three example buttons (Simple English, Academic Text, Chinese paragraph) to see how different writing styles score.
- 9Click the copy button to grab a plain-text report for your notes, docs, or a style guide.
Frequently Asked Questions
What do the readability scores mean?
Each metric measures English reading difficulty from a different angle. Flesch Reading Ease gives a 0–100 score where higher means easier (60–70 is standard newspaper prose). Flesch-Kincaid, Gunning Fog, SMOG, and Coleman-Liau all output a US grade level, roughly the school grade a reader needs to follow the text. The five numbers usually agree on direction but can differ by a few grades because they weigh word length, sentence length, and syllable counts differently.
Which metric should I use?
It depends on your goal: there is no single best one. Flesch Reading Ease is the most intuitive for general copy because the 0–100 scale is easy to reason about. Flesch-Kincaid and SMOG are widely used for education content and school materials. Gunning Fog rewards plain words and short sentences, which makes it a good fit for web writing. The tool shows all five so you can compare rather than trust a single number.
What is a good score?
For Flesch Reading Ease, 60–70 matches standard newspapers and magazines, 70–80 is fairly easy and comfortable for most adults, and 90+ reads like children's books. For the grade-level metrics, the right target is the reading level of your actual audience; grade 6–8 suits general web copy, while specialized documentation can legitimately sit higher. A score is only good relative to who you are writing for.
Does this tool work with Chinese text?
Honestly: the five formulas are defined for English and do not apply to Chinese. When the tool detects that CJK characters dominate the input, it deliberately does not compute English scores. It still shows word, sentence, and character statistics, and it flags Chinese sentences longer than 80 characters, which are the ones readers find hard to follow.
How are syllables counted?
The syllable counter is a heuristic, not a dictionary. It counts vowel groups and applies common rules: silent final e (make, hope), -es and -ed endings that do not add a syllable (hopes, watched), -ed after t or d that does add one (wanted), and consonant-le endings (table). Irregular words can be off by one syllable, which shifts scores by a fraction of a point. The estimate is fine for comparing texts, not for judging a single word.
What counts as a complex word?
Following the Gunning Fog definition, a complex word has 3 or more syllables as counted by the heuristic, words like information, environment, or approximately. The complex word list shows every such word in your text, deduplicated and sorted by syllable count, so you can see at a glance which vocabulary pulls the score up.
How should I use the long-sentence list?
Each listed sentence is over 30 words, which is where readers start losing track. Treat the list as a rewrite queue: split each entry into two or three shorter sentences, then re-check. You will usually see every metric improve at once, because sentence length feeds directly into all five formulas.
Can this tool help with SEO?
Indirectly. Readability is not a direct ranking factor, but hard-to-read pages tend to get lower engagement (readers bounce, skim less, and share less), and those signals matter. A clear, scannable text keeps visitors on the page longer, which is good for SEO in practice. Use the scores as a writing aid, not as a ranking guarantee.
How is this different from the word-counter tool?
Word-counter measures the text itself: word, character, sentence, and paragraph counts plus reading time. This tool interprets the text: it computes readability scores from those measurements, converts them to grade levels, and lists long sentences and complex words. Counting tells you the size; readability tells you the difficulty.
How does this compare to the Flesch-Kincaid checker in Microsoft Word?
Word shows two of the five metrics (Flesch Reading Ease and Flesch-Kincaid Grade Level) under File > Options > Proofing > 'Show readability statistics'. This tool adds Gunning Fog, SMOG, and Coleman-Liau, plus the long-sentence list and complex word list that Word doesn't provide. Scores for the two shared metrics are usually within a point because both count syllables heuristically, but small differences are expected.
What readability level do health and public information guidelines require?
Most plain-language guidelines land in the same zone: the UK NHS and plain English campaigns recommend writing patient information at around age 11 reading age (Flesch-Kincaid grade 5-6), the US Plain Writing Act sets grade 8 as the default for federal documents, and US health literacy guidance suggests grade 5-6 for patient materials. Check your text here and target the band that matches your audience; most consumers of health information sit below grade 8.
Why does mixed Chinese-English text show the Chinese note?
The tool switches to the Chinese note when CJK characters make up at least half of the visible characters. For genuinely mixed text the English formulas are unreliable, so the tool prefers honesty: it shows the word, sentence, and character statistics and skips the scores rather than present numbers that do not mean what they claim.
Why does this readability checker give a different grade level than other tools?
The five formulas weigh word length, sentence length, and syllables differently, so the same text can legitimately score a grade or two apart across metrics and tools. Word's checker only shows two of the five metrics, syllable counting here is heuristic (not dictionary-based), and scores on very short texts (under about 100 words) are statistically unreliable and swing widely. Compare like for like: the same text at a similar length; small gaps are normal, while big gaps usually mean mixed-language input or a very short sample.
Why is my score low even though the text reads fine to me?
Familiarity bias: you know the content, so you don't feel its difficulty. The formulas punish exactly what readers struggle with: long sentences (over 30 words), long words, and jargon, regardless of how clear the topic seems to you. Open the long-sentence list and the complex word list to see precisely what drags the score down, split the offenders, and retest; every metric usually improves at once. Write for your audience's reading level, not for your own.