What is SMOG?
SMOG (Simple Measure of Gobbledygook) is a readability formula that estimates the education level
needed to understand a text. Developed by G. Harry McLaughlin in 1969, it counts polysyllabic words
(3+ syllables) and sentences to produce a grade level from 4th grade through college.
SMOG is particularly recommended for healthcare and patient-facing documents. Many organizations
aim for 8th grade or lower when writing for general audiences.
How the SMOG Formula Works
The SMOG formula counts every word with three or more syllables (polysyllabic words) and the total number of sentences in your sample. It then applies a specific formula to estimate the U.S. grade level needed to comprehend the text. SMOG was designed to be more accurate than earlier formulas when applied to health materials. For best results, use a passage of at least 30 sentences; shorter samples can produce less reliable grades.
When to Use SMOG
Use SMOG when your audience or guideline requires it. Health literacy experts and agencies such as the CDC often recommend SMOG for patient education, consent forms, and consumer health content. Many institutional style guides specify "SMOG 8th grade or below" for public-facing materials. If you need to meet a single readability standard for healthcare or government, SMOG is often the one requested. For a quick comparison with other formulas, use our Combined Readability Checker.
Industry Guidelines and Targets
Health communicators frequently target 6th to 8th grade on the SMOG scale for broad accessibility. Some organizations aim for 5th or 6th grade for high-stakes materials such as medication instructions. Academic or professional documents may sit at 10th grade or above and still be appropriate for their audience. Check your organization's policy; when a SMOG grade is mandated, this calculator helps you hit it.
How to Improve Your SMOG Grade
SMOG responds to polysyllabic words: the more words with three or more syllables, the higher the grade. To lower your SMOG grade, replace long words with shorter synonyms where possible (e.g. "use" instead of "utilize," "help" instead of "assistance"). Shortening sentences also helps, because the formula uses sentence count. Break complex sentences into two or three shorter ones and simplify vocabulary. Then re-run your text through the calculator to see the new grade.
How to Use This Calculator
Paste your text into the box at the top of the page and click the analyze button. You will see your SMOG grade level and a plain-English interpretation. No signup required. For at least 30 sentences, results are most reliable. To see how the same text scores on Flesch-Kincaid, Gunning Fog, and six other formulas, use the Combined Readability Checker linked above.
Other Readability Tools
Get all nine formulas at once: Combined Readability Checker. Or explore individual calculators: Flesch-Kincaid Grade Level,
Gunning Fog Index,
Dale-Chall Readability,
Automated Readability Index,
Coleman-Liau Index,
Linsear Write,
Lix,
Rix,
and the full Readability Calculators hub.
