New Dale-Chall Readability Formula

The New Dale-Chall readability formula calculates the U.S. grade level of a text sample based on sentence length and the number of unfamiliar words. Unfamiliar words are ones that do not appear on a specially designed list of common words that are familiar to most 4th-grade students.

The original familiar word list was only 763 words; however, Professors Chall and Dale extended this list to 3,000 for the revised version of this formula in 1995. Note that the revised version of this formula is what Readability Studio uses.

Because this formula is based on the usage of familiar words (rather than syllable or letter counts), it is often regarded as a more accurate test for younger readers.

Citations

Dale, E. and Chall, J.S. (1948). A Formula for Predicting Readability.

Dale, E. and Chall, J.S. (1995). Readability Revisited: The New Dale-Chall Readability Formula.