Formulas for Measuring Readability of Printed Educational Material 

Readability Measurement Formula for  Printed Educational Material

Flesch Kincaid Scale Formula to Measure Readability

    The Flesch Kincaid formula was developed as an objective
measurement of readability of materials between grade 5 and college level. Its
use has been validated repeatedly over more than 50 years for assessing news
reports, adult educational materials, and government publications. 

    The Flesch
formula is based on a count of two basic language elements: average sentence
length (in words) of selected samples and average word length (measured as
syllables per 100 words of sample). The reading ease (RE) score is calculated
by combining these two variables (Flesch, 1948; Spadero, 1983; Spadero,
Robinson, & Smith, 1980).  

Fog index to Measure Readability

    The Fog formula developed by Gunning (1968) is appropriate for use
in determining the read ability of materials from grade 4 to college level. It
is calculated based on average sentence length and the percentage of
multisyllabic words in a 100-word passage. The Fog index is considered one of
the simpler methods because it is based on a short sample of words (100), it
does not require counting syllables of all words, and the rules are easy to
follow (Spadero, 1983; Spadero et al. , 1980). 

Fry Readability Graph Extended for Printed Educational Material

    The contribution made by the Fry formula derives from the
simplicity of its use without sacrificing accuracy, as well as its wide and
continuous range of testing readability of materials (especially books,
pamphlets, and brochures), which spans grade 1 through college (grade 17 ).
This formula is well accepted by literature and reading specialists and is not
copyrighted (Doak et al., 1996). A series of simple rules can be applied to
plot on a graph two language elements the number of syllables and the number of
sentences in three 100-word selections (Fry, 1968, 1977; Spadero et al., 1980). 

    If a very long text is being analyzed, such as a book containing 50 or more
pages, one should use six 100-word samples rather than three such samples (Doak
et al., 1996). With some practice, this formula takes only about 10 minutes to
determine the readability level of a document. See Appendix A for specific
directions on using the formula and Figure A-1 for the Fry readability graph.

SMOG Formula for Readability Measurement

    The SMOG formula developed by McLaughlin (1969) is recommended not
only because it offers relatively easy computation (simple and fast) but also
because it is one of the most valid tests of readability (Wang et al., 2013).
The SMOG formula measures readability of PEMs from grade 4 to college level
based on the number of polysyllabic words within a set number of sentences
(Doak et al., 1985). 

    It evaluates the read ability grade level of PEMs to
within 1.5 grades of accuracy (Myers & Shepard-White, 2004). Thus, when using
the SMOG formula to calculate the grade level of material, the SMOG results are
usually about two grades higher than the grade levels calculated by the other
methods (Spadero, 1983).

    The SMOG formula has been used extensively to judge grade-level
readability of patient educational materials. It is one of the most popular
measurement tools because of its reputation for reading-level accuracy, its
simple directions, and its speed of use, which is a particularly important
factor if computerized resources for analysis of test samples are not available
(Meade & Smith , 1991; Wang et al., 2013).

    In
summary, Doak et al. (1985) state that it is critically important to determine
the readability of all written materials at the time they are drafted or
adopted by using one or more of the many available formulas. These authors
contend that you cannot afford to “fly blind” by using health materials that
are untested for reading ability difficulty. Pretesting PEMs before
distribution enables the nurse to be sure they fit the literacy level of the
audience for which they are intended. It is imperative that the formulas used
to measure grade-level readability of PEMs are appropriate for the type of
material being tested.