The SMOG index, short for Simple Measure of Gobbledygook, estimates the school grade a reader needs based on how many words of three or more syllables appear in your text. It is the preferred readability formula for health, medical and safety materials because it targets nearly full comprehension rather than a rough average. The formula takes the count of polysyllable words, scales it by 30 divided by the number of sentences, takes the square root, multiplies by 1.043 and adds 3.1291. This calculator counts syllables with a reliable English heuristic and works best on samples of at least 30 sentences, though it will estimate from shorter text too. Results update as you type and everything is computed locally in your browser, so your document stays private and is never uploaded anywhere.
SMOG estimates reading grade from the count of polysyllabic words and is the standard for health and medical readability.
SMOG targets near complete comprehension, which suits health information where readers must fully understand instructions.
A polysyllable word has three or more syllables, and SMOG bases its grade estimate mainly on how many of these appear.
The SMOG index, short for Simple Measure of Gobbledygook, estimates the school grade a reader needs based on how many words of three or more syllables appear in your text. It is the preferred readability formula for health, medical and safety materials because it targets nearly full comprehension rather than a rough average.
Yes. SMOG Index Calculator is completely free, with no sign-up and no usage limits.
Yes. SMOG Index Calculator runs in any modern web browser. There is nothing to download or install.
Yes. SMOG Index Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.