A description of some of the most commonly used readability measures with their determining variables and outputs [6–8]
| Readability measure | Determining variables | Output |
| Flesch reading ease/age | Sentence length Length of words (in syllables) | A score out of 100 (where lower scores indicate more difficult text) and/or reading age |
| Flesch–Kincaid grade level | Sentence length Length of words (in syllables) | US educational grade, or the number of years of education generally required to understand the text |
| Gunning fog index | Average sentence length Prevalence of words that are more than two syllables | US educational grade, or the number of years of education generally required to understand the text |