The original Dale-Chall formula (1948) was developed for adults and children above the 4th grade. They designed it to correct certain shortcomings in the Flesch Reading Ease formula. It uses a sentence-length variable plus a percentage of "hard words" - words not found on the Dale-Chall "long list" of 3,000 easy words, 80 percent of which are known to fourth-grade readers.

To apply the formula:

  1. Select 100-word samples throughout the text (for books, every tenth page is recommended).
  2. Compute the average sentence length in words.
  3. Compute the percentage of words outside the Dale list of 3,000 words.
  4. Compute this equation:

    Score = .1579PDW + .0496ASL + 3.6365

    Where:

    Score = reading grade of a reader who can answer one-half of the test questions on a passage.

    PDW= Percentage of Difficult Words (words not on the Dale-Chall word list)

    ASL = Average Sentence Length in words.

Dale and Chall also published the following chart for correcting the grade-level scores at the higher grades.

Formula Score Corrected Grade Levels
4.9 and below Grade 4 and below
5.0 to 5.9 Grades 5-6
6.0 to 6.9 Grades 7-8
7.0 to 7.9 Grades 9-10
8.0 to 8.9 Grades 11-12
9.0 to 9.9 Grades 13-15 (college)
10 and above Grades 16 and above (college graduate)
Table 5. Dale-Call grade-correction chart.

Of all the formulas produced in the early classic period, validations of this formula have produced the most consistent, as well as some of the highest correlations. It correlated .70 with the multiple-choice test scores on the McCall- Crabbs reading lessons. You can find a computerized version of this original formula online at:

http://www.interventioncentral.org/htmdocs/tools/okapi/okapi.shtml

Those interested in manually applying this formula can find the original 1948 Dale-Chall easy word list online at:

http://www.interventioncentral.org/htmdocs/tools/okapi/okapimanual/dalechalllist.shtml

Robert Gunning and the technique of clear writing Robert Gunning was a graduate of Ohio State University. In 1935, he entered the field of textbook publishing. In the mid-1930s, educators were beginning to see high school graduates who were not able to read. Gunning realized that much of the reading problem was a writing problem. He found that newspapers and business were full of "fog" and unnecessary complexity.

Gunning was among the first to take the new readability research into the workplace. In 1944, he founded the first consulting firm specializing in readability. During the next few years, he tested and worked with more than 60 large city daily newspapers and the popular magazines, helping writers and editors write to their audience.