Dale–Chall readability formula
The Dale–Chall readability formula is a readability test that provides a numeric gauge of the comprehension difficulty that readers come upon when reading a text. It uses a list of 3000 words that groups of fourth-grade American students could reliably understand, considering any word not on that list to be difficult.
The formula was inspired by Rudolf Flesch's Flesch–Kincaid readability test which used word-length to determine how difficult a word was for readers to understand. Edgar Dale and Jeanne Chall instead used a list of 763 words that 80% of fourth-grade students were familiar with, such as "no", "yes", and other such very basic words to determine which words were difficult. The Dale-Chall Readability Formula was originally published in their 1948 article A Formula for Predicting Readability and updated in 1995 in Readability Revisited: The New Dale-Chall Readability Formula, which expanded the word list to 3,000 familiar words.
The formula for calculating the raw score of the Dale–Chall readability score is given below:
If the percentage of difficult words is above 5%, then add 3.6365 to the raw score to get the adjusted score, otherwise the adjusted score is equal to the raw score.
|4.9 or lower||easily understood by an average 4th-grade student or lower|
|5.0–5.9||easily understood by an average 5th or 6th-grade student|
|6.0–6.9||easily understood by an average 7th or 8th-grade student|
|7.0–7.9||easily understood by an average 9th or 10th-grade student|
|8.0–8.9||easily understood by an average 11th or 12th-grade student|
|9.0–9.9||easily understood by an average 13th to 15th-grade (college) student|