What Is the Coleman-Liau Index?
The Coleman-Liau Index is a readability test developed by linguists Meri Coleman and T. L. Liau to help the U.S. Office of Education verify the readability of textbooks in the public school system. The formula calculates the readability score of a text, indicating how easy or hard it is to read in terms of U.S. grade level.
Similar to the Automated Readability Index (ARI), but unlike most other grade-level predictors, the Coleman-Liau Index is calculated from the average characters per word instead of syllables per word, as well as the average number of sentences per 100 words. Although opinions vary, Coleman and Liau believed that word length in letters is a better indicator of readability than word length in syllables. Additionally, character counting is far easier than syllable counting in digital computations, as errors can easily occur with some words when counting syllables.
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 above, and the result will be calculated immediately.
The tool provides a readability score, which can be interpreted as the equivalent U.S. grade level. For instance, if a text receives a Coleman-Liau Index score of 10, it indicates that the text's readability level is suitable for a high school student in the 10th grade.
Please keep in mind that to get a better evaluation of a text's readability, you should also experiment with other readability tests, such as the Flesch Reading Ease test.
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
While readability scores provide a useful indication of a text's readability, they have limitations. The Coleman-Liau Index differs from traditional syllable-based readability indicators by not requiring syllable counts to assess readability.
However, the Coleman-Liau Index does not account for variations in sentence length or word complexity. It also does not consider the difficulty of the subject, sentence structure, vocabulary diversity, or syntax complexity. Additionally, individual reading skills and cultural differences are overlooked. Another limitation of this formula is that it can only be applied to the English language. Texts in other languages must be translated before a comparison can be made.