SMOG Readability Calculator
Calculate the SMOG grade from polysyllabic word counts.
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What is the SMOG readability score?
SMOG (Simple Measure of Gobbledygook) estimates required years of education from a single signal: how many words of three or more syllables appear per 30 sentences. Healthcare publishers rely on it because it predicts comprehension of medical leaflets better than most formulas; the AMA has recommended patient materials score around grade 6. Paste your text to get the grade and the polysyllable count behind it.
How to use the SMOG Readability
- 1 Give it a decent sample; SMOG was designed around 30-sentence chunks.
- 2 Note the SMOG grade and how many polysyllabic words drove it.
- 3 Swap three-syllable words for shorter synonyms where meaning allows.
- 4 Score the edit again and watch the grade fall.
What you can use it for
- Grading patient leaflets and health information.
- Checking safety instructions are widely readable.
- Comparing readability formulas on the same text.
- Meeting plain-language requirements for the public.
Frequently asked questions
What makes a word polysyllabic?
Three syllables or more. “Medication” counts; “medicine” does too; “pill” does not. SMOG counts nothing else, which is exactly why it is easy to act on.
How is the SMOG grade calculated?
Grade equals 1.043 times the square root of (polysyllable count times 30 divided by the sentence count), plus 3.1291. The 30 normalises samples of any length to the original 30-sentence design.
How does SMOG differ from Flesch-Kincaid?
Flesch-Kincaid mixes sentence length with syllables per word; SMOG looks only at polysyllabic words and typically returns a grade one to two levels higher on the same text. Health literacy research generally prefers SMOG.
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