Coleman-Liau Index Calculator

It uses L, letters per 100 words, and S, sentences per 100 words, then computes 0.0588 times L minus 0.296 times S minus 15.8. Longer words push the score up, more sentences per word push it down.

It approximates the US school grade needed to read the text on a first pass. An index near 9 suggests a ninth grade level, while 16 or above points to college or graduate reading.

A letter is any character matching A to Z, a to z or 0 to 9, so spaces and punctuation are ignored. A word is a run of those same characters, which is how the pangram above counts 35 letters across 9 words.

The tool counts groups of period, exclamation mark or question mark. Any non-empty text has at least one sentence, so a passage with no end punctuation is still scored as a single sentence.

Short, plain text with tiny words drives the score down, and a few words of one or two letters can even push it slightly below zero. That is expected behaviour for the formula, not an error.

Coleman and Liau built it for machine scoring. Counting letters is exact and easy to automate, unlike estimating syllables, so the same text always yields the same index.

Both are character based and return a US grade, and this page shows them side by side. They weight letters and sentence length differently, so the two scores usually land close but rarely match exactly.

The on-page card rounds the index to one decimal place, so the pangram reads 3.8. The JSON API returns the same value at full precision if you need the extra digits.

Yes. The score is computed in your browser as you type, and nothing you paste is uploaded, logged or stored anywhere.