Flesch–Kincaid readability test

The Flesch–Kincaid readability test, composed of the Flesch Reading Ease and Flesch–Kincaid Grade Level tests, are designed to indicate comprehension difficulty when reading something in English.

In Flesch Reading Ease, higher test scores mean that the material is easier to read, while lower scores signify a harder read. The equation for this test is:



Scores can be interpreted like this:
90.0–100.0 = easily understandable by an average 11-year-old student
60.0–70.0 = easily understandable by 13- to 15-year-old students
0.0–30.0 = best understood by university graduates

The Flesch-Kincaid Grade Level test is the same thing but instead of using a scale of 0-100, it uses a number that corresponds to the grade level at which students should be able to understand the text. Obviously, this is used much more in the field of education.

The formula for this is:



There are several other readability tests, but Reading Ease is used by the U.S. Department of Defense for its documents and forms, and Microsoft Word. I stumbled upon the Flesch–Kincaid readability test today when I was fiddling with Google Docs.