Like other popular readability tests, the Bormuth Readability Index calculates a reading grade level required to read a text based on two factors: 1) character count (average length of characters) rather than syllable count; and 2) average number of familiar words in the sample text. The Bormuth Readability Index uses the Dale-Chall word list to count familiar words in samples of text. Initially, Professor John R. Bormuth of the University of Chicago developed this formula to evaluate academic documents and school textbooks. This formula works reliably on texts above 4th grade level.

Typically, the Bormuth Readability Index outputs a grade level that closely matches the adjusted grade level from the new Dale-Chall Readability Formula. The differences between the two formulas are that the Bormuth Readability Index relies on character count instead of syllable count; and instead of calculating a percent of difficult words, it calculates the average of familiar words in the text.

The Bormuth Readability Index is sometimes called The Bormuth Formula, the Bormuth Grade Level Formula, or Degrees of Reading Power. (The Bormuth Readability Index was adapted into the Degrees of Reading Power used by the College Entrance Examination Board in 1981.)

The Bormuth Readability Index outputs a number that correlates to a U.S. grade level. For example, a result of 10.6 means students in 10th grade and above can read and comprehend the text. Unlike the new Dale-Chall Readability Formula which outputs an adjusted number that you must match to a number on an adjusted grade level table, the Bormuth Readability Index does not require you to use a table to determine an adjusted grade level.