The Fog Index helps educators determine a student's reading level.
This is a system that has been developed to judge the reading level of a text. It is calculated in three steps:
1. From several randomly-selected samples of about 100 words divide the number of words in the total sample by the number of complete thought sentences to get average sentence average. Count every independent clause (separated by colons, commas, and semicolons) as a thought sentence.
2. Count the number of “hard” words having three of more syllables. Do not count as “hard” words the following: proper nouns, compound words made from shorter words (e.g., basketball), or verb forms whose third syllable ends in “ed” or “es” (e.g., “decided”). Count the syllables as they are generally pronounced, not as the dictionary divides them. If the same word is repeated, count it again. Divide the number of hard words by the total number of words in the sample. The figure should be computed to four decimal places. (In order to avoid a distorted result, terms such as “nuclear magnetic resonance” should be counted as “NMR.”)
3. Add the end number from 1 and 2 together and multiply by 0.4. This will give the grade level of the reading sample.