Gunning Flog Index
In linguistics, the Gunning fog index is a readability test for English writing. The index estimates the years of formal education a person needs to understand the text on the first reading. For instance, a fog index of 12 requires the reading level of a United States high school senior (around 18 years old). The test was developed in 1952 by Robert Gunning, an American businessman who had been involved in newspaper and textbook publishing.
The fog index is commonly used to confirm that text can be read easily by the intended audience. Texts for a wide audience generally need a fog index less than 12. Texts requiring near-universal understanding generally need an index less than 8.
| Fog | Index Reading level by grade |
|---|---|
| 17 | College graduate |
| 16 | College senior |
| 15 | College junior |
| 14 | College sophomore |
| 13 | College freshman |
| 12 | High school senior |
| 11 | High school junior |
| 10 | High school sophomore |
| 9 | High school freshman |
| 8 | Eighth grade |
| 7 | Seventh grade |
| 6 | Sixth grade |
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