Jun 22

The Coleman-Liau Index is a readability test that determines the understandability of a document. As you can calculate the Coleman-Liau Index on Joe’s Web Tools, we now explains you the working of the index and the history behind it.

The Coleman-Liau Index determines the measurement in difficulty going through and understanding a portion of text by a person. It forms the base of an estimate in US grade level, which is used as a mandate for the students to read, understand and interpret the text.

Designed by Meri Coleman and T.L.Liau, the test rests on characters per words in the document, rather than on syllables, as in the case of other readability tests like the Flesch-Kincaid and Gunning Fog Index. This makes the test more computer friendly, as characters per words is more easily and accurately counted by automated programs than syllables.

The Coleman-Liau index uses the following formula:

Coleman-Liau Index

In a text of 100 words, the number of characters is divided by the number of words and the answer is multiplied by 5.89 (A). For the second step, the number of sentences per 100 words is multiplied by 0.3 (B). To obtain the index, B is subtracted from A, and then further subtracted by 15.8. The answer indicates the US grade level of the document.