Coleman-Liau Readability Formula

The Coleman-Liau readability formula calculates the U.S. grade level of a text sample based on sentence lengths and number of characters.

Coleman-Liau is meant for secondary age (4th grade to college level) readers. This formula is based on text from the .4 to 16.3 grade level range. This test usually yields the lowest grade when applied to technical documents

The Coleman-Liau Formula

First, calculate the estimated Cloze percentage with the following formula:

ECP = 141.8401 - (.214590*C) + (1.079812*S)

Then convert the Cloze percentage into a U.S. grade level with the following formula:

GL = (-27.4004*(ECP/100)) + 23.06395

Where:

ECP	Estimated Cloze %
GL	U.S. grade level
C	Number of characters
S	Number of sentences

Note that a simplified version of this formula is also available, although it yields slightly less accurate precision:

GL = ((5.88*C)/W) - ((29.5*S)/W) - 15.8

Where:

GL	U.S. grade level
W	Number of words
C	Number of characters
S	Number of sentences

This test requires a 100-word sample; however, note that Readability Studio always analyzes your entire document to guarantee the most accurate results and does not use subsamples for any of its test calculations. If a formula requires a subsample of a specific size, then standardization is used.

Citations

Coleman, M. and Liau, T.L. (1975). 'A computer readability formula designed for machine scoring', Journal of Applied Psychology, 60, No. 2, 283-284.