Coleman-Liau index calculator
Estimates the US school grade needed to understand English text. It counts letters instead of syllables, so results are consistent.
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How to use it
- Enter text.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
Index = 0.0588 × L − 0.296 × S − 15.8, where L is the average letters per 100 words and S is the average sentences per 100 words.
Example
Result: Coleman-Liau index: 19.17; Letters per 100 words: 666.67; Sentences per 100 words: 14.29.
Limits and caveats
- English only; non-Latin words are ignored.
- Very short texts give unstable results; use 100 words or more.
Questions about this tool
How does Coleman-Liau differ from Flesch?
Flesch depends on an estimated syllable count, while Coleman-Liau counts letters directly, so its result is exactly repeatable.
How do I read the result?
The number approximates a US school grade, so 10 means text suited to about a 10th grade student.
Are digits counted as letters?
No. Only the Latin letters A to Z go into L; digits and punctuation do not.