Currently, the readability scores for program materials are measured using the Flesch-Kincaid Grade Level. Developed by Rudolf Flesch and J. Peter Kincaid, the Flesch-Kincaid readability scores are among the most widely used and heavily tested measures of readability. The Flesch-Kincaid grade level test uses average word length and average sentence length to calculate the American school grade you would need to comprehend the material on the page.
Prior to November 2022, the readability scores were calculated by taking the average of multiple methods (SMOG, Fog, and Fry). "SMOG" (Statistical Measure of Gobbledygook) is used to measure the readability of documents that have 30 or more sentences. The score is based on the number of "big" words (words with three or more syllables) in three-10 sentence passages. SMOG measures a document at a minimum of a fourth grade reading level. "Fog" is used to measure the readability of documents that have less than 30 sentences. The score is determined by the average sentence length and percentage of three-or-more-syllabic-words in the entire passage. "Fry" measures readability of a document based on the average number of sentences and syllables of three-100 word passages.