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Free SMOG Calculator for PDFs & Text

Upload a PDF or paste English text to calculate its SMOG grade level and see how easy your material is to read.

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Upload your PDF, wait for the text to finish processing, then select Calculate SMOG to see its reading level. Include at least three sentences; 30 or more gives a more reliable estimate.

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What is SMOG readability?

SMOG estimates the U.S. reading grade needed to understand English prose. It uses the number of words with three or more syllables and the number of sentences to help you judge whether your writing fits your audience.

Learn about readability metrics

How is the score calculated?

SMOG Grade = 1.043 x √(polysyllabic words x 30 / sentences) + 3.1291

Polysyllabic words have three or more syllables, and each occurrence counts. SMOG was calibrated on 30-sentence samples. This calculator uses your whole passage and scales the counts to 30 sentences; shorter passages give a rough estimate.

How should I use the result?

Readability evaluators offer a starting point. Your readers’ background knowledge, the subject, and the way you organize information also affect how easy a text is to understand.