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{{Use mdy dates|date=June 2015}}
{{No footnotes|date=January 2017}}

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 1953 in Spache's "A new readability formula for primary-grade reading materials," (''The Elementary School Journal'', 53, 410–413), and has subsequently been revised.

==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.

The original formula was: 
:<math>
\mbox{Grade Level} = \left ( 0.141 \times \mbox{Average sentence length} \right ) + \left ( 0.086 \times \mbox{Percentage of unique unfamiliar words} \right) + 0.839
</math>

The revised formula is: 
:<math>
\mbox{Grade Level} = \left ( 0.121 \times \mbox{Average sentence length} \right ) + \left ( 0.082 \times \mbox{Percentage of unique unfamiliar words} \right) + 0.659
</math>

==Further reading==
*{{cite journal
 | author = Spache, G.
 | year = 1953
 | title = A New Readability Formula for Primary-Grade Reading Materials
 | journal = The Elementary School Journal
 | volume = 53
 | issue = 7
 | pages = 410–13
 | doi = 10.1086/458513
| jstor=998915
| s2cid = 145135468
 }}
* Clarence R. Stone. "Measuring Difficulty of Primary Reading Material: A Constructive Criticism of Spache's Measure." ''The Elementary School Journal'', Vol. 57, No. 1 (Oct. 1956), pp. 36–41

{{Readability tests}}

[[Category:Readability tests]]