The ColemanLiau Readability Formula
(also known as The ColemanLiau Index
) is a readability assessment test designed by linguists Meri Coleman
and T. L. Liau
to approximate the usability of a text. Coleman said he created the formula as one of the many ways to help the U.S. Office of Education calibrate the readability of all textbooks for the public school system. Like other popular readability formulas, the ColemanLiau Index approximates a U.S. grade level to understand the text.
Similar to the Automated Readability Index
, but unlike most of the other grade-level predictors, the ColemanLiau
relies on characters instead of syllables per word. Instead of using syllable/word and sentence length indices, Meri Coleman and T. L. Liau believed that computerized assessments understand characters more easily and accurately than counting syllables and sentence length.
Meri Coleman and T. L. Liau developed this formula to automatically (by computer) calculate samples of hard-copy text, instead of manually hard-coding the text. Unlike syllable-based readability indicators, it does not require
you to analyze the characters that create the words (such as syllable counts) only their length in characters. Therefore, you can scan a hardcopy of text into your word processor, use a free OCR program to recognize character, word, and sentence boundaries, and apply this formula to the text. According to Coleman, "There is no need to estimate syllables since word length in letters is a better predictor of readability than word length in syllables." You calculate the ColemanLiau Index with the following formula
is the average number of letters per 100 words. S
is the average number of sentences per 100 words. As an example, let's use this abstract from a public domain book: The best things in an artists work are so much a matter of intuition, that there is much to be said for the point of view
that would altogether discourage intellectual inquiry into artistic phenomena on the part of the artist. Intuitions are shy things and apt to disappear if looked into too closely. And there is undoubtedly a danger that too much knowledge and training may supplant the natural intuitive feeling of a student, leaving only a cold knowledge of the means of expression in its place. For the artist, if he has the right stuff in him ...
The abstract contains 4 sentences, 100 words, and 448 letters or digits; L
is 448 and S
is 4. Formula: CLI = 0.0588 x 448(L) - 0.296 x 4.0(S) - 15.8 = 10.6
Therefore, this formula grades this abstract of text at a grade level of 10.6
, or roughly appropriate for a 10-11th grade high school student
. The ColemanLiau Index
grades this entire article (with the sample text) a 14.9
, which is appropriate for a college-level undergraduate student in the U.S.
Although we used just 100 words for the sample above, you should input at least 300 words of text to calculate a more accurate grade score.