SMOG Readability Formula

The SMOG[1] formula is a recommended[2] and tested[3] method for grading the readability of written materials. The method is quick, simple to use and particularly useful for shorter materials, e.g., a study's information pamphlet or consent form. To calculate the SMOG reading level, begin with the entire written work 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. If the text has fewer than 30 sentences, use as many as are provided.
   
2. Count the number of words containing 3 or more syllables (polysyllabic), including repetitions of the same word.
   
3. Look up the approximate grade level on the SMOG conversion table below:

When using the SMOG formula:

• A sentence is defined as a string of words punctuated with a period, an exclamation mark, or a question mark. Consider long sentences with a semi-colon as two sentences.
  
• Hyphenated words are considered as one word.
  
• Numbers which are written should be counted. If written in numeric form, they should be pronounced to determine if they are polysyllabic.
  
• Proper nouns, if polysyllabic, should be counted.
  
• Abbreviations should be read as though unabbreviated to determine if they are polysyllabic. However, abbreviations should be avoided unless commonly known.
• If the written piece being graded is shorter than 30 sentences, approach it as follows:
• Count all of the polysyllabic words in the test.
• Count the number of sentences.
• Find the average number of polysyllabic words per sentence, i.e.:
  Total # of polysyllabic words
  Average = Total # of sentences
• Multiply that average by the average number of sentences short of 30.
• Add that figure on to the total number of polysyllabic words.
• Compare the number of polysyllabic words in the SMOG conversion table.
  

Spanish Readability Formulas

Crawford, A.N. (March 1984). A Spanish language Fry type readability procedure: Elementary level. Los Angeles: Bilingual Education Paper Series, Evaluation Dissemination and Assessment Center, California State University, Los Angeles, 7:1-17.

Garcia, W.F. (1976). Assessing readability for Spanish as a second language: The Fry graph and cloze procedure. Unpublished doctoral dissertation, Teachers College, Columbia University.

Gilliam, B., Pena, S.C., and Mountain, L. (1980). "The Fry graph applied to Spanish readability." The Reading Teacher, 33:426-430.

Spaulding, S. (1956). "A Spanish Readability formula." The Modern Language Journal. 40:433-441.

Spaulding, S. (1951). "Two formulas for estimating the reading difficulty of Spanish." Educational Research Bulletin, 30:117-124

Acknowledgment
Thanks to Dr. Mary S. Neumann, DHAP, NCHSTP, for her research of SMOG and her assistance based on her wide use of the method to improve the readability of materials produced by CDC or through CDC grant support. Thanks also for her research of the Spanish language formulas which appear in the guide "Developing Effective Educational Print Materials" which she authored with the TEB, DSTDP, NCHSTP.

Readable Replacement Words/Phrases for Polysyllabic Terms Common to CDC Consent Forms

1. Developed by Harold C. McGraw, Office of Educational Research, Baltimore County Schools, Towson, MD.

2. Doak, Cecilia C., Leonard G. Doak, and Jane H. Root (1995). Teaching Patients with Low Literacy Skills. New York: J.B. Lippincott Co. 36-59.

3. Ibid: page 59 cites a 1979-81 test of the method conducted by Patient Learning Associates, Inc., of Potomac, Maryland, in which the SMOG formula performed exceptionally when used to grade materials presented to 291 individuals graded by accepted methods as having reading levels between the 4th and 16th grades.