The FORCAST Readability Formula is the result of The Human Resources
Research Organization of Alexandria, Virginia, to study the reading requirements of
military occupational specialties in the US Army. John S Caylor, Thomas G Sticht, and J
Patrick Ford were assigned this responsibility in 1973. The subjects for the research were
Vietnam draftees entering basic training and job-specific training. The FORCAST
Readability Formula evolved from their study. The formula was first published in 1973 as
an article in a journal called Literacy Discussion, published by UNESCOs International
Institute for Adult Literacy.
The FORCAST Readability Formula is the only test not designed for running
narrative. Therefore, it is considered perfect for multiple-choice quiz contests,
applications, entrance forms, and so on. The FORCAST Readability Formula is strictly
not prescribed for assessing primary age reading materials.
The FORCAST Readability Formula
Step 1: Select a sample text of 150 words.
Step 2: Count N, i.e., the number of single-syllable words in the sample text.
Step 3: Divide N by 10.
Step 4: Subtract the result obtained in Step 3 from 20.
The mathematical formula is:
GL = 20 (N/10)
GL = Grade Level
N = Number of monosyllabic words in the sample text.
Step 4: The Reading Age can be calculated by applying the formula:
Reading Age = 25 (N/10) years
However, if the sample text contains 100 words, the Reading Age = 25 (N/6.67)
This formula was validated at only a 35% score on comprehension tests.
In a follow-up study in 1979, Lydia Hooke and her colleagues validated the use of
the FORCAST formula on technical regulations for the Air Force. They also found that
four of the seven writers of the regulations underestimated the grade level of their
materials by more than one grade.
Due to its relative ease of use, The US Air Force, in 1977, approved the use of
FORCAST Readability Formula to write understandable publications.