SMOG Index
A grade-level formula designed for healthcare and safety content. Requires 30+ sentences.
SMOG (Simple Measure of Gobbledygook) was created by G. Harry McLaughlin in 1969. It was designed for healthcare and safety material, where accuracy matters more than convenience. Formula: 1.0430 × √(polysyllables × 30/sentences) + 3.1291. SMOG counts only words with 3+ syllables and scales them to a 30-sentence sample. It's considered more accurate than Flesch-Kincaid for predicting 100% comprehension (vs. the typical 50–75% threshold of other formulas). For short samples under 30 sentences, SMOG results are less reliable.