What is the primary purpose of the Gunning Fog Index?

The primary purpose of the Gunning Fog Index is to assess the readability level of a text. This formula estimates the years of formal education needed to understand a piece of writing on the first reading. It considers both the average sentence length and the percentage of complex words (words with three or more syllables) in the text. By generating a numerical score, the index helps writers and editors determine if their material is accessible to their intended audience, guiding them to adjust the complexity as necessary to improve comprehension. This focus on readability is essential for effective communication, particularly in professional and educational settings where the audience's understanding is critical.