liminfoReadability Score Checker
Free web tool: Readability Score Checker
About Readability Score Checker
The Readability Calculator analyzes English text against four established readability formulas simultaneously: Flesch Reading Ease (206.835 − 1.015 × ASL − 84.6 × ASW), Flesch-Kincaid Grade Level (0.39 × ASL + 11.8 × ASW − 15.59), Coleman-Liau Index (0.0588 × L − 0.296 × S − 15.8, where L is average letters per 100 words and S is average sentences per 100 words), and the Automated Readability Index (4.71 × chars/word + 0.5 × words/sentence − 21.43). Displaying all four formulas at once lets you cross-validate your text complexity rather than relying on a single metric.
Content writers, technical authors, educators, and compliance teams use multi-formula readability analysis to make more confident decisions about text difficulty. Different formulas weight syllables, characters, and sentence length differently, so comparing them reveals whether the complexity of your text is driven by long sentences, multisyllabic vocabulary, or both. The Coleman-Liau and ARI formulas, which count characters rather than syllables, are particularly useful because they do not depend on a syllable-counting algorithm and tend to be more consistent across different word types.
All calculations are performed client-side using React's useMemo hook, so results update instantly as you type without any server request. The syllable counter used for the Flesch formulas applies suffix-stripping rules (removing silent "ed", "es", and trailing "e" patterns) before counting vowel groups, resulting in improved accuracy over a naive vowel-count approach. Word, sentence, and syllable statistics are displayed together with the four grade-level scores in a compact grid layout.
Key Features
- Four readability formulas computed simultaneously: Flesch Reading Ease, Flesch-Kincaid, Coleman-Liau, and ARI
- Live summary statistics: total words, sentences, syllables, and Flesch Reading Ease label
- Formula strings displayed under each score for educational transparency
- Suffix-stripping syllable counter with improved accuracy over simple vowel counting
- Flesch Reading Ease interpreted with 7-level label (Very Easy to Very Difficult)
- Coleman-Liau and ARI use character counts — no syllable ambiguity
- Instant recalculation on every keystroke via React useMemo optimization
- 100% client-side processing — no text is ever sent to a server
Frequently Asked Questions
What is the difference between the four readability formulas?
Flesch Reading Ease uses syllable and sentence length to produce a 0–100 score (higher = easier). Flesch-Kincaid Grade Level converts that same data into a U.S. grade equivalent (lower = easier). Coleman-Liau uses average letters per 100 words and average sentences per 100 words, avoiding syllable counting entirely. The Automated Readability Index (ARI) uses a character-to-word ratio and a word-to-sentence ratio, making it the most straightforward to compute mechanically. All four formulas output roughly comparable grade levels for normal English prose.
Why do the four scores sometimes disagree?
Each formula weights sentence length and word complexity differently. A text with long sentences but simple vocabulary may score a high Flesch ease but a high Flesch-Kincaid grade. A text with short sentences but long technical words may have a low Coleman-Liau but a normal Flesch ease. Comparing all four scores gives a fuller picture: if they all agree, you can be confident in the grade level; if they disagree significantly, your text has uneven complexity.
What is the Coleman-Liau Index?
The Coleman-Liau Index was developed by Meri Coleman and T.L. Liau in 1975 as a formula that could be computed by optical character recognition machines, which could count letters and sentences but not syllables. The formula is: 0.0588 × (average letters per 100 words) − 0.296 × (average sentences per 100 words) − 15.8. It outputs a U.S. grade level estimate similar to Flesch-Kincaid.
What is the Automated Readability Index (ARI)?
The ARI was developed in 1967 for the U.S. Air Force to monitor the readability of technical manuals in real time on typewriters. Its formula is: 4.71 × (characters/words) + 0.5 × (words/sentences) − 21.43. Like Coleman-Liau, it uses character counts rather than syllable counts, making it well-suited for automated text analysis pipelines where syllable detection is impractical.
How does the syllable counter work in this tool?
The syllable counter first lowercases the word and removes non-alphabetic characters, then strips common silent suffixes ("ed", "es", and trailing silent "e" patterns using regular expressions) before counting vowel groups (sequences of aeiouy). It also treats words of zero length as zero syllables and returns a minimum of 1 for any non-empty word. This suffix-stripping approach is more accurate than naive vowel counting for most English words.
What text should I paste for the most useful results?
Paste at least 100–200 words of representative content. Readability formulas are statistical averages and become unreliable on very short samples — a single sentence can produce wildly fluctuating scores because the averages have very little data to smooth over. For the most stable results, analyze complete paragraphs or entire documents rather than individual sentences or titles.
Can I use this calculator for non-English text?
All four formulas in this calculator are calibrated for English text. The Flesch and Flesch-Kincaid formulas rely on English syllable patterns, while Coleman-Liau and ARI use character counts that are alphabet-size-dependent. Applying these formulas to Korean, Chinese, Japanese, or other non-Latin scripts will produce meaningless scores. Use language-specific readability tools for non-English text.
What grade level should I target for different content types?
General web content and news articles: grade 6–9. Marketing and consumer-facing copy: grade 5–8. Academic journal articles: grade 12–16. Legal contracts: grade 10–14 (though plain-language initiatives push for grade 8 or lower). Medical patient education materials: grade 6–8 for broad comprehension. Children's books: grade 1–4. Using this calculator to verify your content falls in the intended range helps ensure your audience can read and retain your message.