Coleman–Liau index calculator
Grade 8 or lower for general audiences. Because it counts letters, it is consistent across tools: there is no syllable guesswork.
0 / 20,000 characters · saved in this browser only · upload a PDF or screenshot to pull out its text
Coleman–Liau Index
—
Formula: 0.0588 × L − 0.296 × S − 15.8 (L = letters per 100 words, S = sentences per 100 words)
- Words
- 0
- Sentences
- 1
- Letters and digits
- 0
How to read the Coleman–Liau score
| Score | Meaning |
|---|---|
| 5 or below | Very easy: understood by most 10–11 year olds |
| 6–8 | Plain English: the target for email, web copy and public information |
| 9–10 | Fairly difficult: fine for engaged professional readers |
| 11–12 | Difficult: typical of specialist reports |
| 13–16 | College level: academic and technical writing |
| 17+ | Graduate level: legal and scientific text |
Lower scores mean easier text.
Where the Coleman–Liau Index comes from
Proposed by Meri Coleman and T. L. Liau in 1975 so that readability could be computed by machines that counted characters easily but not syllables.
Other readability formulas
- Flesch–Kincaid Grade Level: 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
- Flesch Reading Ease: 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
- Gunning Fog Index: 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
- SMOG Index: 1.043 × √(polysyllables × 30 ÷ sentences) + 3.1291
- Automated Readability Index: 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43
Questions people ask
Why does Coleman–Liau use letters instead of syllables?
Letters can be counted exactly by software, while syllables have to be estimated. Word length in letters tracks word difficulty closely enough for a reliable grade estimate.
Is Coleman–Liau more accurate than Flesch–Kincaid?
Neither is “more accurate” in general; they measure similar things. Coleman–Liau is more consistent between tools because it avoids syllable estimation.