Raygor readability estimate

The Raygor estimate graph is a readability metric for English text.

It was developed by Alton L. Raygor, who published it in 1977.

[1] The US grade level is calculated by the average number of sentences and letters per hundred words.

These averages are plotted onto a specific graph where the intersection of the average number of sentences and the average number of letters/word determines the reading level of the content.

[2] This graph is primarily used in secondary education to help classify teaching materials and books into their appropriate reading groups.