The New Dale-Chall Formula improves the original Dale-Chall Readability Formula as expounded in A Formula for Predicting Readability in 1948. The creators of this formula were Edgar Dale and Jeanne Chall.
Dale and Chall created The Dale-Chall Formula for adults and children above 4th grade as a way to improve upon the Flesch Reading Ease Formula. The Dale-Chall Formula was unique because, unlike other formulas that use word-length to assess word difficulty, the Dale-Chall Formula uses a count of 'hard' words. The Dale-Chall Formula calculates the US grade level of a text sample based on sentence length and the number of 'hard' words. These 'hard' words are words that do not appear on a specially designed list of common words familiar to most 4th-grade students.