Spache Readability Formula

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The Spache Readability Formula is a readability test for writing in English, designed by George Spache. It works best on texts that are for children up to fourth grade. For older children, the Dale-Chall Readability Formula is more appropriate.

It was introduced in 1952 in Spache's "A new readability formula for primary-grade reading materials," (The Elementary School Journal, 53, 410-413), and has subsequently been revised.

1 Calculation
2 References
3 Further reading
4 External link

[edit] Calculation

The method compares words in a text to a set list of everyday words. The number of words per sentence and the percentage of unfamiliar words determine the reading age.

ASL = Average sentence length
UW = Number of unique unfamiliar words
GL = U.S. grade level

The original formula was:

$\mbox{Grade Level} = \left ( 0.141 \times \mbox{Average sentence length} \right ) + \left ( 0.086 \times \mbox{Number of unique unfamiliar words} \right) + 0.839$

The revised formula is:

$\mbox{Grade Level} = \left ( 0.121 \times \mbox{Average sentence length} \right ) + \left ( 0.082 \times \mbox{Number of unique unfamiliar words} \right) + 0.659$