Free Readability Checker
Score your content with 6 readability formulas — Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, ARI and Coleman-Liau. See which sentences to rewrite. No sign-up required.
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6 Formulas
Sentence Highlighting
Works on Mobile
Your Content
Minimum 100 words recommended for meaningful scores. Longer content gives more accurate results.
Readability Report
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FRE
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Paste at least 100 words on the left to see your readability score.
Flesch Ease
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FK Grade
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Gunning Fog
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SMOG
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ARI
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Coleman-Liau
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What Is Readability?
Readability measures how easy a piece of text is to read and understand. It's not about the topic itself — it's about sentence length, word complexity and structure. Two articles about quantum physics can have the same subject but wildly different readability.
Higher readability generally means more engaged readers, longer time on page, lower bounce rate and better conversion. That's why almost every popular blog and news site targets an 8th–9th grade reading level, even when writing for adults.
The 6 readability formulas
- Flesch Reading Ease (FRE) — 0 to 100, higher is easier. The most-used metric. Formula:
206.835 − 1.015 × ASL − 84.6 × ASW, where ASL is average sentence length and ASW is average syllables per word. - Flesch-Kincaid Grade Level — converts FRE into a U.S. school grade. Formula:
0.39 × ASL + 11.8 × ASW − 15.59. - Gunning Fog Index — estimates years of formal education needed. Formula:
0.4 × (ASL + 100 × complex word ratio), where "complex" means 3+ syllables. - SMOG Index — Simple Measure of Gobbledygook. Strictest formula; requires ≥30 sentences to be reliable. Formula:
1.0430 × √(30 × complex words / sentences) + 3.1291. - Automated Readability Index (ARI) — based on characters, not syllables. Formula:
4.71 × (characters / words) + 0.5 × (words / sentences) − 21.43. - Coleman-Liau Index — also character-based. Formula:
0.0588 × L − 0.296 × S − 15.8, where L is letters per 100 words and S is sentences per 100 words.
What's a good Flesch Reading Ease score?
- 90–100: Very easy — 5th grade (comics, tabloids)
- 80–89: Easy — 6th grade (mass-market fiction)
- 70–79: Fairly easy — 7th grade (blogs, popular magazines)
- 60–69: Standard — 8th–9th grade (the sweet spot for SEO content)
- 50–59: Fairly difficult — 10th–12th grade (quality journalism)
- 30–49: Difficult — College (academic, legal)
- 0–29: Very confusing — College graduate (bureaucratic, technical)
For most web content, aim for 60–70. That's clear enough for casual readers, but rich enough to not feel dumbed down.
How to improve readability
- Shorten sentences. Aim for 15–20 words on average. Anything over 30 words is hard to follow — split it.
- Use simpler words. "Utilise" → "use". "Commence" → "start". "Approximately" → "about". Replace 3-syllable words with shorter alternatives when possible.
- Use active voice. "The team wrote the report" reads faster than "The report was written by the team".
- One idea per sentence. If a sentence covers two concepts, split it into two.
- Break long paragraphs. 2–4 sentences per paragraph. On mobile, even shorter.
- Add subheadings. They help scanning and break up visual monotony.
- Use bullet points and numbered lists. Lists are faster to read than prose.
- Read it out loud. If you stumble, your reader will too.
Common readability mistakes
- Chasing the highest score. A 95 FRE is not always better — some topics need nuance that shorter words can't provide. Aim for the right level for your audience.
- Ignoring the sample size. SMOG and Gunning Fog need at least 30 sentences to be reliable. Short paragraphs give noisy scores.
- Splitting sentences that shouldn't be split. Don't turn one coherent idea into three choppy fragments just to hit a target.
- Dumbing down technical content. For developer docs, an FK grade of 10–12 is fine. Don't strip precision for simplicity.
- Forgetting about international audiences. If your readers are non-native English speakers, aim 5–10 points higher on FRE.
Frequently Asked Questions
What is a good readability score?
For web content and blog posts, aim for a Flesch Reading Ease score of 60–70 — equivalent to an 8th–9th grade reading level. This is what most popular blogs and news sites target. Technical documentation can go slightly lower (50–60). Content for kids or mass-market audiences should be 80+.
What is Flesch Reading Ease?
Flesch Reading Ease (FRE) is a formula developed by Rudolf Flesch in 1948 that measures how easy a text is to read. It uses average sentence length and average syllables per word. Scores range from 0 (very difficult) to 100 (very easy).
What is a good grade level for SEO content?
Aim for grade 7–9 (Flesch-Kincaid Grade Level). This corresponds to Flesch Reading Ease 60–70. Google does not directly rank easier content, but readers engage more with content that's easy to scan and understand.
How is readability different from keyword density?
Keyword density measures how often a keyword appears in your content. Readability measures how easy your content is to read and understand. Both matter for SEO — you want content that's clearly on-topic AND a pleasure to read. Use our Keyword Density Checker for the first and this tool for the second.
What is a complex word?
In readability formulas like Gunning Fog and SMOG, a complex word is defined as a word with 3 or more syllables — excluding proper nouns, familiar names and words ending in common suffixes like -ed and -es. Replacing these with simpler alternatives dramatically improves readability.
Why do my Flesch and grade level scores disagree?
Different formulas emphasise different things. Flesch Reading Ease weighs syllables heavily, while ARI and Coleman-Liau use characters instead. When scores disagree, trust the average — or focus on the specific score that matches your target audience (e.g. Flesch for general readers, SMOG for healthcare/legal content).
Is this readability checker free?
Yes — 100% free, no sign-up, runs entirely in your browser. Your content never leaves your device.