Readability Score Checker
Paste any text and get 6 professional readability scores instantly: Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog Index, SMOG, Coleman-Liau, and Automated Readability Index. Browser-based, private, free.
Flesch Reading Ease
Grade Levels
Text Stats
📖 What This Tool Does
A free online readability checker that calculates six professional readability metrics from any text you paste: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog Index, SMOG Index, Coleman-Liau Index, and the Automated Readability Index (ARI). These are the same metrics used by Yoast SEO, Hemingway Editor, Grammarly, and professional content editors worldwide.
Everything runs in your browser — your text is never sent to a server. Perfect for writers targeting a specific audience, SEO marketers optimizing blog content, teachers grading student work, editors simplifying technical documentation, or anyone who wants to know how accessible their writing actually is.
📏 The Six Metrics Explained
Flesch Reading Ease
0-100 scale where higher = easier. Developed by Rudolf Flesch in 1948. Most widely used readability metric in the world. 60-70 = standard magazine level; 80+ = elementary.
Flesch-Kincaid Grade
US school grade level. Developed for the US Navy to rate technical manuals. A score of 8 means a typical 13-year-old can understand it. Target 6-8 for general web audiences.
Gunning Fog Index
Years of formal education needed to understand the text. Heavily penalizes words with 3+ syllables. Good for identifying "dense" writing. Target 7-9 for broad accessibility.
SMOG Index
"Simple Measure of Gobbledygook" — designed specifically for healthcare materials. Based on the square root of polysyllable count. Estimated years of education needed.
Coleman-Liau Index
Uses characters instead of syllables, so it's more reliable for computer-counted text. Produces a US grade level. Great for comparing computer-generated content.
Automated Readability Index
Also uses characters and sentence length. Originally designed to pick books for US school grades. Commonly referenced alongside Flesch-Kincaid for cross-validation.
🎯 Target Scores by Use Case
| Use case | Flesch Ease | FK Grade |
|---|---|---|
| Children's books | 80-90 | 3-5 |
| General web / blog posts | 60-70 | 6-8 |
| Marketing / sales copy | 65-75 | 6-7 |
| Newspapers | 60-70 | 7-9 |
| Technical blogs | 50-60 | 10-12 |
| Academic papers | 30-50 | 13-16 |
| Legal documents | 20-40 | 16+ |
🔒 Privacy
- ✓ All calculations run in your browser using JavaScript
- ✓ Your text is never sent to any server
- ✓ No storage, no logging, no tracking
- ✓ Works offline after the page first loads
❓ Frequently Asked Questions
What is a readability score?
A readability score is a numerical measure of how easy a piece of text is to read and understand. Scores are typically expressed as a US school grade level (e.g., "grade 8" means a 13-year-old can understand it) or as a 0-100 ease score (higher = easier). Professional writers, editors, content marketers, and teachers use these scores to match writing to their audience.
What is a good readability score?
For general audiences (magazines, blogs, marketing copy), aim for Flesch Reading Ease of 60-70 and Flesch-Kincaid Grade of 6-8. For technical content aimed at specialists, 30-50 ease and grade 10-12 is normal. For children's content, target 80+ ease and grade 1-4. Plain-language government writing guidelines recommend grade 8 or lower.
How is the Flesch Reading Ease calculated?
Flesch Reading Ease = 206.835 − 1.015 × (words/sentences) − 84.6 × (syllables/words). Shorter sentences and shorter words produce higher (easier) scores. Developed by Rudolf Flesch in 1948, it is the most widely used readability metric in the world.
What is the difference between Flesch-Kincaid Grade and Flesch Reading Ease?
Flesch Reading Ease gives a 0-100 score (higher = easier). Flesch-Kincaid Grade converts that to a US school grade level (lower = easier). They use the same input (sentence length and syllable count) but express the result differently. Grade Level is often more intuitive for writers targeting a specific age or education level.
Why do different formulas give different scores?
Each formula weights sentence length and word complexity slightly differently and was designed for different purposes. Flesch-Kincaid was designed for the US Navy to rate technical manuals. Gunning Fog emphasizes "complex words" (3+ syllables). SMOG was designed for healthcare materials. Coleman-Liau uses characters instead of syllables (more accurate for computer-counted text). Looking at multiple metrics gives a more complete picture than relying on any single one.
Is my text private?
Yes. All calculations happen entirely in your browser using JavaScript. Your text is never sent, stored, or logged anywhere. Close the tab and everything is gone.
Does this work for languages other than English?
Partially. The syllable-counting algorithm is tuned for English, so metrics like Flesch and Gunning Fog are most accurate for English text. Character-based metrics like Coleman-Liau work reasonably well for other Latin-script languages. For non-Latin scripts (Chinese, Arabic, etc.), these formulas don't apply — readability uses different conventions in those languages.
Can I use this to improve my SEO content?
Yes. Search engines like Google and Bing reward content that matches the reading level of its intended audience. For general web audiences, aim for Flesch-Kincaid grade 7-9. For technical blogs, grade 10-12 is fine. The readability metrics here are the same ones used by tools like Yoast SEO, Hemingway Editor, and Grammarly.