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]

A rendition of the Raygor Graph.

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. Note that this graph is very similar to the Fry readability formula's graph.^[2]

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

The formula

• Extract a 100-word passage from the selection.^[2] If the material is long, take a subsample from the beginning, middle, and end.
• Count the number of sentences in each passage. Count a half sentence as 0.5.
• Count the number of words in each passage containing six or more letters.
• Find the point on the Raygor estimate graph.