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How to Use the SMOG Readability Formula on Health Literacy Materials

A number of readability formulas can help you assess the literacy level of printed communications; however, the SMOG Readability Formula (Simple Measure of Gobbledygook) is a popular method to use on health literacy materials.

SMOG Readability Formula

1.  Count 10 consecutive sentences near the beginning of the text that you want to assess, 10 in the middle, and 10 near the end. Count as a sentence any string of words ending with a period, question mark, or exclamation point.

2.  In the 30 selected sentences, count every word of three or more syllables. Any string of letters or numbers beginning and ending with a space or punctuation mark should be counted if you can distinguish at least three syllables when you read it aloud in context. If a polysyllabic word is repeated, count each repetition.

3.  Estimate the square root of the number of polysyllabic words counted. Take the square root of the nearest perfect square. For example, if the count is 95, the nearest perfect square is 100, which yields a square root of 10. If the count lies roughly between two perfect squares, choose the lower number. For instance, if the count is 110, take the square root of 100 rather than that of 121.

4.  Add 3 to the approximate square root. This gives the SMOG Grade, which is the reading grade that a person must have to understand your text.

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

SMOG Readability Formula

Online calculators will do this assessment for you. Just go to jsp and cut and paste your text into the calculator.

Assessing Pre-Existing Communication Materials

Although it is easier to create materials for specific literacy levels, it is also likely you may want to adapt existing materials for your own use. Use the following assessment guide to determine if you should use an existing material or to develop one yourself. It is also a helpful tool to refer to as you develop your own materials.


  • Is the information accurate and up-to-date?
  • Does it focus on the key, most necessary information? (And avoid extraneous information?)
  • Have any important points been left out?
  • Are concrete examples given to illustrate general ideas?
  • Does the content take the audience's culture and circumstances into account?
  • Does the material call on the reader to take some specific, appropriate action?


  • Is there a clear core message, supported by a few (3-4) main points?
  • Is the information presented in easy-to-understand "chunks" or sections?
  • Are the main points presented in a logical order that will make sense to the audience?
  • Are headers used to direct the reader to the main points?
  • Is there a summary of key points?

Source Credibility

  • Does the material's author/producer have credibility with the target audience?
  • Does the spokesperson or other source shown in the material have credibility with the target audience?

Language and Tone

  • Is everyday language used?
  • Are action words and the active voice used?
  • Is the tone friendly and conversational, with the reader treated as a partner?
  • Does the material use short words and short sentences, without sounding choppy?
  • Are unfamiliar terms, abbreviations, and acronyms defined?
  • If slang or figures of speech are used, does the target audience know their meaning?
  • What reading level does readability testing show?
  • Does the material avoid preaching, condescending, or blaming?
  • Does the material avoid using fear tactics?

Cultural Competence

  • Is the material written in the preferred language of the target audience?
  • If translated, is the translation accurate and well-done?
  • Are demeaning labels or stereotypes avoided?
  • Is the material appropriate for the audience's age and gender?
  • Does the material show respect for the target audience's values, customs, beliefs, and prior knowledge?
  • Are the people depicted representative of the target audience?


  • Do design elements (like headers, bullets, and boxes) help draw attention to the main points? Does the material have an accessible, open look with plenty of white space?
  • Is the font (typeface) clear and clean, and large enough (12 points or larger)?
  • Do visuals support the text and are they placed close to the text they relate to?
  • Do visuals show the correct way to do something?
  • Are confusing graphs, charts, and statistics avoided?
  • Is there good contrast between paper and ink?
  • Is the material visually attractive?

Overall Impression

  • What are the strengths of the material?
  • hat are the weaknesses of the material?

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