Gunning Fog Index Calculator

Around 7–8 reads as plain English that near-universal audiences can follow. Most professional writing targets under 12; popular magazines sit around 9–11, while academic prose often exceeds 16. Lower is easier, but the right score depends on your readers.

Fog = 0.4 × (words ÷ sentences + 100 × complex words ÷ words). Complex words have three or more syllables, not counting proper nouns, familiar hyphenated compounds, or words whose third syllable comes from a common -es, -ed or -ing ending.

The arithmetic is exact, but syllables are counted with a heuristic (as every automated Fog tool does), and proper nouns are detected by capitalization, so scores can differ slightly from a hand count. Differences are usually well under one grade level.

Both estimate a school grade, but Fog counts the share of long words while Flesch–Kincaid uses average syllables per word. Fog tends to punish long-word-heavy prose harder. Running both gives you a more reliable picture than either alone.

Gunning's original method sampled passages of about 100 words. Anything shorter is legitimate to measure but noisier — a single long sentence can swing the index by several points.