The Dale–Chall formula identifies the percentage of unfamiliar words and produces a grade-level score.
Use Dale–Chall when your audience is children, English learners, or general adults reading material outside their expertise. Because it scores familiarity (not syllable count), it catches problems that other formulas miss — like "epistemology" vs. "knowledge".
Dale–Chall is the only mainstream formula that scores vocabulary familiarity. Compared to Flesch–Kincaid it is much more sensitive to word choice and much less sensitive to sentence length. Pair it with Flesch–Kincaid for a balanced view.
The Dale-Chall formula compares your text against a fixed list of approximately 3,000 "familiar" words that 80% of 4th-graders know.
Words not on the list are considered "difficult." The formula combines the percentage of difficult words with average sentence length.
This implementation uses the New Dale-Chall (1995) revision with 2,942 words, courtesy of the open-source `dale-chall` package.
A list of approximately 3,000 words that 80% of 4th graders are familiar with. We use the New Dale-Chall (1995) revision with 2,942 words.
Dale-Chall is conservative. Suffixes (-ed, -ing) are stripped before matching, but uncommon spellings, regional words, and most proper nouns count as unfamiliar.
A raw Dale-Chall score of 5.0–5.9 means easily understood by 5th–6th graders. Marketing and consumer text typically target 6.0–6.9.
Input
The pedagogical efficacy of constructivist methodologies remains contested.
Output
Dale–Chall Score: 11.4 — College graduate.
Six of seven words are not on the Dale–Chall familiar-words list. The high "unfamiliar word" ratio combines with the single long sentence to produce a graduate-level score.
Classic 0–100 readability score.
readabilityU.S. grade level for your text.
readabilityPenalises complex (3+ syllable) words.
readabilityHealth & medical text grade level.