Coleman–Liau Index calculator
Coleman–Liau uses letters per word instead of syllables, because a computer can count letters exactly while syllable counting is always an estimate. The result is a US grade level.
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The Coleman–Liau Index formula
0.0588 × L − 0.296 × S − 15.8 (L = letters per 100 words, S = sentences per 100 words)
Long words and long sentences both push the score up; more sentences per 100 words pull it down.
Meri Coleman and T. L. Liau published it in 1975. They designed it to be computed by machine, counting characters instead of syllables.
What your score means
| Score | Reading level |
|---|---|
| 1–5 | Elementary |
| 6–8 | Middle school |
| 9–12 | High school |
| 13–16 | College |
| 17+ | Graduate |
Drag the inputs, watch the score
The formula only “sees” these numbers. Change them and notice which one moves the score most.
Grade level (higher = harder)
10.2
US grade 10
At 18 words per sentence there are 5.6 sentences per 100 words (S).
Questions people ask
Why use Coleman–Liau instead of Flesch–Kincaid?
It avoids syllable counting, which even good software gets wrong for some words. That makes it more consistent between tools, although it can over-rate texts full of long but familiar words.
What are L and S in the formula?
L is the average number of letters per 100 words; S is the average number of sentences per 100 words.
Can the Coleman–Liau index be negative?
Yes, for very short words in very short sentences, such as early reader books. Treat anything below 1 as kindergarten level.