SMOG Index Calculator
The SMOG Index is the standard readability formula for healthcare and public health writing. Paste your text below — requires 30+ sentences for full accuracy.
Breakdown
What Is the SMOG Index?
How it works
SMOG stands for Simple Measure of Gobbledygook. Developed by G. Harry McLaughlin in 1969, it estimates the years of education needed to understand a piece of writing based entirely on the count of polysyllabic words (3+ syllables).
Why 30+ sentences?
The SMOG formula was designed and validated using samples of exactly 30 sentences. With fewer sentences, the polysyllabic word count becomes statistically unreliable. For short texts, other formulas like Flesch-Kincaid give more accurate results.
Healthcare standard
The American Medical Association and the National Institutes of Health recommend the SMOG Index for evaluating patient education materials. The target for health communications is typically Grade 6 or below to reach the broadest audience.
How to Improve Your SMOG Score
Reduce polysyllabic words
SMOG is driven entirely by words with 3+ syllables. Replace medical jargon with plain language equivalents: "high blood pressure" instead of "hypertension," "heart attack" instead of "myocardial infarction."
Define when you can't simplify
Some technical terms can't be replaced. In those cases, introduce the term with a plain-language explanation on first use. This won't lower your SMOG score but improves actual comprehension for readers.
Test with your audience
SMOG is a starting point, not a guarantee. Even a low SMOG score doesn't mean patients will understand health information — cultural context, health literacy, and prior knowledge all play a role beyond what formulas can measure.