Coleman-Liau Index Definition

The Coleman-Liau Index is a readability test that tries to look at how difficult a text is to understand and to express that as the grade level a student in the USA would need to be able to read it.

While some readability tests use the number of syllables, the Coleman-Liau Index uses the number of characters in words, which is more easily calculated, but some say is less accurate.

To calculate it, the following steps are taken:

  1. Divide the number of characters by the number of words, and multiply by 5.89. Call this A.
  2. Take the number of sentences in a fragment of 100 words, and multiply by 0.3. Call this B.
  3. Subtract B from A and subtract 15.8

Coleman-Liau Index = (5.89 * characters/words) − (0.3 * sentences /(100 * words)) − 15.8

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