The Dale-Chall Readability formula
Raw = 0.1579 × (% difficult words) + 0.0496 × (words ÷ sentences), + 3.6365 if difficult words > 5%- Percentage of words not on the Dale-Chall list of familiar words
- Average sentence length
What it counts
We check each word against the 1995 familiar-word list (2,942 entries, from the MIT-licensed “dale-chall” dataset). Following the counting rules, regular plurals, -ed, -ing, -er and -est forms of listed words, proper names and numbers count as familiar.
What score to aim for
A raw score under 5 reads at grade 4 or below; 7–8 is high-school level; 9+ is college.
| Raw score | Reading level |
|---|---|
| 4.9 and below | Grade 4 and below |
| 5.0–5.9 | Grades 5–6 |
| 6.0–6.9 | Grades 7–8 |
| 7.0–7.9 | Grades 9–10 |
| 8.0–8.9 | Grades 11–12 |
| 9.0–9.9 | College |
| 10.0 and above | College graduate |
Limits to keep in mind
We use the 1948 regression equation with the 1995 word list, the combination most software reports. The 1995 book also offers a table-based procedure that can differ slightly. The list reflects American children’s vocabulary; British spellings may be flagged as unfamiliar.
Where it comes from
Edgar Dale and Jeanne Chall published the formula in 1948 at Ohio State University. Instead of word length, it asks whether a word is on a list of words most fourth-graders know. Chall and Dale revised the list in 1995 to about 3,000 words.
Source: Dale, E., & Chall, J. S. (1948). “A formula for predicting readability.” Educational Research Bulletin, 27(1), 11–20; Chall, J. S., & Dale, E. (1995). Readability Revisited: The New Dale-Chall Readability Formula. Brookline Books.
How we count syllables, sentences and words, and how our numbers compare on test passages, is documented in Readability formulas explained.