Dale-Chall Readability Formula

A readability formula first published by Edgar Dale and Jeanne Chall in 1948 and revised in 1995. Unlike formulas that rely only on surface counts, Dale-Chall compares every word in a text against a manually curated list of "easy" words familiar to fourth-grade readers; the raw score combines the percentage of difficult words (words not on the list) with average sentence length. Because the word list encodes real reader familiarity rather than syllable counts, Dale-Chall often correlates better with comprehension than Flesch-Kincaid, SMOG, or Gunning Fog Index, and it is commonly used in healthcare and plain-language work. Its main limitations are the cost of curating and updating the word list, and its insensitivity to syntactic or discourse complexity.