How is the Forcast score calculated?
Forcast is designed to include content that is not in sentence form, i.e. images, links, lists, forms, etc. Thus, it does not factor sentence-length into the calculation of readability scores. Instead, the number of one-syllable words found in a chunk of 150 words is the only variable measured.
Forcast Grade Level = 20 - (# of one-syllable words out of 150 words / 10)
Forcast requires the count of one-syllable words to be done in 150-word chunks of text. Of course, not all Web pages will have text in multiples of 150 words. Therefore, the Forcast analysis reports the total number of words on the Web page but analyzes readability based on the following conditions:
- when the Web page analyzed has exactly 150 (or exact multiples of 150) words, all the one-syllable words on the page are used in calculating the score.
- when the Web page analyzed has more than 150 words (or multiples of 150 words), the total words sampled is cut off at the last (multiple-of-) 150-word mark. For instance, for a Web page with 550 total words, only the first 450 words (i.e. 3 sets of 150) is analyzed by the tool. Thus, only the one-syllable words in the identified sample of 450 words is used in calculating the score.
- when the Web page analyzed has less than 150 total words, all the one-syllable words are used in calculating the score. However, as the formula assumes there is a sample of 150 words, the number of one-syllable words is proportionally adjusted.
Results
The score obtained translates into a numerical grade, e.g. a score of 9.8 is equivalent to 9th grade reading level in the United States.