Powers, Sumner, Kearl Readability Formula

The Powers, Sumner, Kearl readability formula calculates the U.S. grade level of a text sample based on sentence length and number of syllables.

Powers, Sumner, Kearl is used for primary age (Kindergarten to 7th grade) readers. This test is not suitable for secondary age books, and is best meant for material in the 7-10 age range.

The PSK Formula

GL = (ASL * .0778) + (NS * .0455) - 2.2029 

Where:

GL	U.S. grade level
ASL	Average sentence length
NS	Number of syllables per 100 words

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

Powers, R.D., Sumner, W.A., and Kearl, B.E. (1958). 'A recalculation of four adult readability formulas',Journal of Educational Psychology, University of Wisconsin, Vol. 49, No. 2 , 99-105.