The Dale–Chall formula identifies the percentage of unfamiliar words and produces a grade-level score.
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.
Classic 0–100 readability score.
readabilityU.S. grade level for your text.
readabilityPenalises complex (3+ syllable) words.
readabilityHealth & medical text grade level.