Gunning Fog Index Calculator

How it is calculated

Paste English text. The tool counts W words (anything separated by whitespace), S sentences (each run of ., ! or ?; at least 1) and C complex words, then computes:

Fog = 0.4 × (W / S + 100 × C / W)

A word counts as complex when it has three or more syllables. The tool estimates syllables by counting groups of consecutive vowels (a, e, i, o, u, y) in the letters of the word and dropping one for a silent final e. Only the letters a to z are looked at, so digits, punctuation and accented letters are ignored. It does not exclude suffixes or proper nouns, so it can overcount. The index is rounded to two decimals and roughly corresponds to a US school grade.

Common mistakes

• Running non-English text through it. Only plain a to z letters are examined, so Turkish and other accented text is mis-scored and short words may be counted wrongly.
• Pasting text with abbreviations or decimals such as "e.g." or "3.5", which create extra sentence endings and lower the words-per-sentence part.
• Pasting a few words with no full stop. It counts as one sentence, so a title or a heading scores very differently from the full text.
• Treating the score as exact. The syllable count is an estimate, so "approved" and similar words are flagged complex and the figure is a guide, not a verdict.
• Trying to lower the score only by chopping sentences. Complex-word density counts for as much as sentence length.