What Is the Coleman-Liau Index Calculator?
The Coleman-Liau Index Calculator determines the readability of a text based on the Coleman-Liau Index formula. Simply paste or upload your text into the text box to get your score.
The Coleman-Liau Index is only one interpretation of text readability. See our Flesch Reading Ease Calculator to compare alternative results.
What Is the Coleman-Liau Index?
The Coleman-Liau Index was developed by linguists Meri Coleman and T. L. Liau. It calculates the readability score of a text aligned with U.S. grade level. For example, a Coleman-Liau score of 6 means the text can be understood by an average reader in 6th grade.
Unlike many other readability formulas, the Coleman-Liau Index uses the average number of characters (not syllables) per word and the average number of sentences per 100 words to assess readability. This makes it easier to calculate for digital texts, where counting characters is more straightforward than counting syllables.
How to Calculate the Coleman-Liau Index Score
The readability formula for calculating the Coleman-Liau Index score uses the number of letters (including digits), word count, and sentence count in a text:
0.0588 × (letters ÷ words) × 100 - 0.296 × (sentences ÷ words) × 100 - 15.8
As the formula shows, a higher score indicates that the text is more difficult to read.
Limitations of the Coleman-Liau Index Formula
The Coleman-Liau Index gives one estimate of readability, but it relies on averages and does not capture how complex a subject is for the reader or how familiar the vocabulary might be. As a result, it might under-score technical texts with relatively short words or over-score texts with longer words that are still commonly understood.
Coleman-Liau was also designed for English-language texts and may not be reliable for other languages.
Related Tools
- Dale-Chall Readability: Check readability using the Dale-Chall formula based on familiar words.
- Fry Readability Calculator: Estimate reading grade level using the Fry readability formula.