How to Test for Readability
The SMOG Readability Formula
To calculate the SMOG reading grade level, begin
with the entire written work that is being
assessed, and follow these four steps:
1. Count off 10 consecutive sentences near the
beginning, in the middle, and near the end of
2. From this sample of 30 sentences, circle all
of the words containing three or more
syllables (polysyllabic), including repetitions
of the same word, and total the number of
3. Estimate the square root of the total number
of polysyllabic words counted. This is done
by finding the nearest perfect square, and
taking its square root.
4. Finally, add a constant of three to the square
root. This number gives the SMOG grade, or
the reading grade level that a person must
have reached if he or she is to fully
understand the text being assessed.
A few additional guidelines will help to clarify
§ A sentence is defined as a string of words
punctuated with a period (.), an exclamation
point (!) or a question mark (?).
§ Hyphenated words are considered as one
§ Numbers which are written out should also be
considered, and if in numeric form in the text,
they should be pronounced to determine if
they are polysyllabic.
§ Proper nouns, if polysyllabic, should be
§ Abbreviations should be read as unabbreviated
to determine if they are polysyllabic.
Not all pamphlets, fact sheets, or other printed
materials contain 30 sentences. To test a text that
has fewer than 30 sentences:
1. Count all of the polysyllabic words in the text.
2. Count the number of sentences.
3. Find the average number of polysyllabic words
per sentence as follows:
Total # of polysyllabic words
Total # of sentences
4. Multiply that average by the number of
sentences short of 30.
5. Add that figure on to the total number of
6. Find the square root and add the constant of 3.
Perhaps the quickest way to