FogCalc™
Check Your Content's Readability Score with our Gunning Fog Index Calculator. Use our free readability calculator to measure how clear and accessible your writing is. The Fog Index helps optimise content for your target audience by analysing sentence length and word complexity.
The Gunning Fog Index was developed in 1952 by Robert Gunning, a pioneering American businessman who worked with newspapers and publishing companies. He noticed that many written materials were too complex for their intended audiences - creating a "fog" of confusion that readers had to navigate through.
Gunning created this readability formula while running his consulting firm, Robert Gunning Associates, which helped writers at newspapers like Wall Street Journal and Newsweek create clearer content. The formula gained widespread adoption because it effectively measured how "foggy" or unclear writing was, helping writers produce more accessible content.
Today, the Gunning Fog Index remains one of the most respected and widely-used readability measures, used by content creators, educators, and organizations worldwide to ensure their writing reaches and engages their intended audience effectively.
The Fog Index helps measure how readable your content is. A high score indicates complex writing that may be hard to understand, while a lower score suggests clearer, more accessible content. This calculator makes it easy to check your text's readability.
Fog Index = 0.4 × (words per sentence + percentage of complex words)
What it measures:
Words per sentence: Average number of words between punctuation marks
Complex words: Words with three or more syllables (excluding proper nouns, familiar jargon, and compound words)
Percentage: The portion of complex words relative to total word count
Interpreting your score:
Under 10: Easy to read
10-12: Ideal for most audiences
13-16: Fairly difficult
Above 17: Difficult for most readers
Example: A typical news article might score 11-12, while academic papers often score 15-17. For web content aimed at a general audience, aim for a score under 12.
Simply paste your text into the calculator below to check its readability score.
Why Use a Fog Index Calculator? Clear, readable content is essential for engaging your audience and improving SEO performance. By understanding and optimizing your content's readability score, you can:
Increase reader engagement and time on page
Reduce bounce rates
Improve content accessibility
Enhance user experience
Support better SEO rankings
