Free Readability Checker — Flesch-Kincaid & More
Check your text's readability score instantly with six industry-standard formulas including Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau, and ARI — all free, all in your browser.
Flesch-Kincaid, Gunning Fog, SMOG, Coleman-Liau & ARI — all free, all instant.
Paste your text below and click Analyze. Perfect for writers, students, content marketers, and anyone who wants to match their writing to their target audience's reading level.
Last updated: May 18 2026
Reviewed by the QuickTooly Team
Readability Guide
Why Check Your Text's Readability?
- Match your audience: Know whether your writing is pitched at the right reading level for your readers.
- Six formulas at once: Flesch Reading Ease, Flesch-Kincaid Grade, Gunning Fog, SMOG, Coleman-Liau, and ARI — all calculated instantly.
- SEO-friendly writing: Search engines favour clear, accessible content. A Flesch score above 60 generally signals well-structured copy.
- 100% private: Your text never leaves your browser. No server uploads, no data collection.
- Completely free: All formulas, no paywalls, no account required.
Understanding the Readability Formulas
Flesch Reading Ease
The most widely used readability formula. Scores range from 0 (extremely difficult) to 100 (very easy). A score of 60–70 is considered plain English suitable for the average adult. Most web copy should aim for 60+. The formula penalises long sentences and words with many syllables.
Flesch-Kincaid Grade Level
Converts the same factors as Flesch Reading Ease into a U.S. school grade level (e.g. 8 = 8th grade). Used by the U.S. Department of Defense as a writing standard. Aim for grade 8 or below for general audiences.
Gunning Fog Index
Estimates the years of formal education required to understand the text on the first read. A score of 12 corresponds to a U.S. high school senior. Most business writing should target a Fog score below 12. The formula focuses heavily on the proportion of "complex" words (three or more syllables).
SMOG Index
Simple Measure of Gobbledygook — widely used in health communication. Like Gunning Fog, it counts complex words, but uses a square-root formula that tends to produce higher grade estimates. Most accurate with 30+ sentences.
Coleman-Liau Index
Unique in that it uses character counts rather than syllable counts, making it easier to compute programmatically. It correlates well with the Flesch-Kincaid Grade Level and outputs a U.S. grade level estimate.
Automated Readability Index (ARI)
Also character-based, originally developed for the U.S. Air Force. ARI tends to agree closely with Coleman-Liau and Flesch-Kincaid. Output is a grade level; add 5 to estimate the minimum reader age.
Tips for Improving Readability
- Shorten your sentences: Aim for an average of 15–20 words per sentence. Long sentences are the single biggest driver of poor scores.
- Choose shorter words: Replace multi-syllable words with simpler alternatives where meaning isn't lost.
- Use active voice: Passive constructions add words and complexity without adding clarity.
- Break up paragraphs: Shorter paragraphs reduce cognitive load and improve perceived readability even without changing scores.
- Aim for a target audience: Blog posts and web copy: Flesch 60–70. Academic writing: 30–50. Children's content: 80+.
Frequently Asked Questions
What is a good Flesch Reading Ease score?
For general web content and marketing copy, aim for 60–70 (plain English, accessible to adults). Scores above 80 are appropriate for consumer-facing writing; scores below 30 are typical of legal, scientific, or technical documents.
Which readability formula should I use?
Flesch Reading Ease and Flesch-Kincaid Grade Level are the most universally accepted. For health or medical content, SMOG is the standard. When working with non-English text or automated systems, Coleman-Liau and ARI (both character-based) are often preferred.
Does a lower grade level always mean better writing?
Not always. Grade level should match your audience. Academic papers, legal contracts, and technical documentation are expected to score high. The goal is to match the text's complexity to your readers' needs, not to minimise the score at all costs.
How accurate is the syllable counting?
Syllable counting in any browser-based tool is an approximation based on vowel-group patterns. Results are accurate for standard English prose and will agree with professional tools within ±5% for most texts. Proper nouns, technical terms, and non-English words may skew counts slightly.
Is my text stored or sent anywhere?
No. All analysis runs entirely in your browser using JavaScript. Your text is never transmitted to any server, stored in any database, or shared with any third party. You can safely paste confidential or sensitive content.
How much text do I need for accurate results?
Most formulas are reliable with 100+ words. The SMOG index is designed for texts with at least 30 sentences; for shorter texts its estimate will be marked as approximate. For best results, paste at least a full paragraph.