The Dale-Chall Word List contains approximately three thousand familiar words that are known in reading by at least 80 percent of the children in Grade 5. It gives a significant correlation with reading difficulty. It is not intended as a list of the most important words for children or adults. It includes words that are relatively unimportant and excludes some important ones.
When 80 percent of the fourth-graders indicated that they knew a word, the Dale-Chall Formula
appended the word to the list. This arbitrary cutting off at the 8o-percent point and the lack of measuring the importance of these words help in appraising the ease or difficulty of material. For purposes of computing a level of difficulty, however, the percentage of words outside this list is a very good index of the difficulty of reading materials. The terms familiar and unfamiliar describing words are used here in a statistical sense. There is, however, a real place for a list of important familiar words, graded in about four levels, to help prepare materials for adults of limited
The formula was created by Edgar Dale and Jeanne S. Chall. It was published in 1948 in their book "A formula for predicting readability."
Here is the full 3,000 words which comprise the Dale-Chall word list: