What Is the Coleman-Liau Index?

The Coleman-Liau Index is a readability test developed by linguists Meri Coleman and T. L. Liau to calculate the readability score of a text, helping to determine if the text is easy or hard to read.

Unlike syllable based readability indicators, the Coleman-Liau Index relies on the average number of characters per word and the average number of sentences per 100 words. This makes it more similar to the Automated Readability Index.

What Is the Coleman-Liau Index Calculator?

This Coleman-Liau Index Calculator determines the readability of a text based on the Coleman-Liau Index formula.

The tool provides a readability score, which can be interpreted as the corresponding U.S. grade level equivalent. For instance, if a text receives a Coleman-Liau Index score of 13.4, it indicates that the text's readability level is suitable for a first-year college student.

If you need a better predictor which is used more, you may want to check out the Flesch-Kincaid readability test, which is also used in public school system a lot.

How to Calculate the Coleman-Liau Index Score

The readability formula for calculating the Coleman-Liau Index score uses the number of letters (digits included), word count (word length), and sentence count in a text.

0.0588 × (letters ÷ words) × 100 - 0.296 × (sentences ÷ words) × 100 - 15.8

According to the Coleman-Liau Index formula, a higher score indicates that the text is more challenging to read. Therefore, as with other readability tests, more complex sentences generally result in a higher score, and lower readability.