The SMOG Readability Formula

The SMOG Readability Formula

 

The SMOG Readability Formula

To calculate the SMOG reading grade level, begin with the entire written work that is being assessed, and follow these steps:

 

  1. Count off 10 consecutive sentences near the beginning, in the middle, and near the end of the text.

 

  1. 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 words circled.

 

  1. 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.

 

  1. 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.

 

The general rule of thumb is to aim materials for a 6th-grade reading level or lower.

Online calculators will do this assessment for you. Just go to http://www.wordscount.info/hw/smog. jsp and cut and paste your text into the calculator.

 

A few additional guidelines will help to clarify these directions:

 

  • 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 word.
  • 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.
  • 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 (3 or more syllables) words in the text.

 

  1. Count the number of sentences.

 

  1. Find the average number of polysyllabic words per sentences as follows:

Average =       Total number of polysyllabic words

Total number of sentences

 

  1. Multiply that average by the number of sentences short of 30.

 

  1. Add that figure on to the total number of polysyllabic words.

 

  1. Find the square root and add the constant of 3.

 

 

The SMOG (Simple Measure of Gobbledygook) Readability Index

Many tools are available to measure the readability of your document. One is the SMOG Readability Index. It is a simple technique that can be used to assess the grade level of a document. First, count the number of words with three or more syllables in a chain of 30 sentences in your draft. Then look up the approximate grade level on the following chart.

SMOG Conversion Table*

Total Polysyllabic Word Count Approximate Grade Level
0-2

3-6

7-12

13-20

21-30

31-42

43-56

57-72

73-90

91-110

111-132

133-156

157-182

183-210

211-240

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

* Developed by Harold C. McGraw, Office of Educational Research, Baltimore County Schools, Towson, Maryland.