Readability checker — 5 formulas, instant analysis
Paste any text and instantly see how readable it is. We compute five industry-standard readability formulas simultaneously, plus sentence stats, vocabulary diversity, and grade-level interpretation.
- Flesch Reading Ease + 4 grade-level formulas
- Sentence length and complexity analysis
- Vocabulary diversity and complex-word counts
- Runs entirely in your browser — no signup
What a readability checker actually measures
Readability is a statistical property of text. Formulas approximate it by sampling structural signals: how long the sentences are, how many syllables per word, what fraction of words are polysyllabic. These signals correlate well with how hard real readers find a text — not perfectly, but well enough to be useful.
The five formulas we compute are:
- Flesch Reading Ease — outputs 0–100. Higher is easier. Score 60+ is comfortable for most adults.
- Flesch-Kincaid Grade Level— outputs a US grade number. 8.5 means “average 8th grader can read this.”
- SMOG Index — focuses on polysyllabic words. Sensitive on shorter passages where syllable counts are noisier.
- Coleman-Liau Index — uses character count instead of syllables. More reliable for technical text and any content where syllable heuristics fail.
- Automated Readability Index (ARI) — character- and sentence-length based, originally tuned for typewritten text. Useful as a sanity check on Coleman-Liau.
How to interpret your scores
Look at the spread, not just one number. If Flesch says “easy” but Coleman-Liau says “college,” you probably have a few long technical terms throwing off the syllable count. Inspect the longest sentence and the most-complex words flagged by the analyzer.
For most use cases, target a Flesch Reading Ease of 60–75: comfortable for general audiences, professional without being stilted. Push higher (80+) for landing pages and marketing copy. Allow lower (40–55) for technical content where precision must beat simplicity.
How to improve readability fast
- Cut sentences over 25 words. Almost always two clearer sentences hiding in one bloated one.
- Swap polysyllabic words.“Utilize” → “use.” “Subsequently” → “then.” “Facilitate” → “help.”
- Vary sentence rhythm. A 15-word sentence then a 4-word punch reads better than two 12-word sentences.
- Use lists. Bulleted lists score better on readability and engagement.
- Cut filler.“Really very actually” earns nothing.
When readability checking matters most
Three situations where running this check before publishing is high-leverage:
- Newsletter and blog content.Open and read rates correlate strongly with grade level — lower grade level, higher engagement. (Most A/B tests show a 5–15% lift when dropping from grade 12 to grade 8.)
- SEO content.Google’s helpful-content updates favor pages that match user intent and reading level. Top-ranking pages for most queries cluster around grade 7–9.
- Product copy and onboarding. Every reading friction in onboarding costs you activated users. Re-run this tool after every copy iteration.