SMOG Index

A readability formula calibrated for healthcare and patient-education writing.

SMOG ("Simple Measure of Gobbledygook") is a grade-level readability formula introduced by G. Harry McLaughlin in 1969. Formula: 1.043 × √(complex_words × 30/sentences) + 3.1291. Tends to score higher (more conservative) than Flesch–Kincaid; widely used in healthcare communication.

Related terms

  • Readability — How easy a text is to read, typically measured by sentence length and word complexity.
  • Gunning Fog Index — A readability formula that emphasises polysyllabic words; designed for business writing.
  • Flesch–Kincaid Grade Level — A readability formula expressed as a US school grade — grade 8 means an eighth-grader could read it.