Spache Readability Formula
Spache Readability Formula is one method of finding out how hard a piece of writing is (its textual difficulty).
The method compares words in a text to a list of words which are familiar in everyday writing. The words that are not on the list are called unfamiliar. The number of words per sentence are counted. This number and the percentage of unfamiliar words is put into a formula. The result is a reading age. Someone of this age should be able to read the text.
Spache works best on texts that are for children under the age of eight.
the formula; (0.141 * average sentence length)+(0.086 * percentage of difficult words)+0.839 = grade level
According to Oleander Solutions ([1]), the revised Spache Formula is:
GL = (.121 * ASL) + (.082 *UW) + .659
Where:
GL = U.S. grade level ASL = Average sentence length UW = Number of unique unfamiliar words