To check the readability of any document, several formulas have been devised since the 1920’s. As Joe’s Web Tools offers an online text readability calculator that include the Flesch reading ease and the Flesch–Kincaid grade level test, we will present those tests in this article.
Of these, two were created by Rudolph Flesch who published his works in the 1940’s on English usage and vocabulary. In 1943, Flesch published his dissertation ‘Marks of a Readable Style’. This laid the groundwork for his readability formula that could be applied on adult reading material. Publishers realized that his formula could help them reach an audience 40% to 60% larger.
By 1948, Flesch had prepared two formula. The Reading Ease Formula suggested the dropping of affixes and the usage of only two variables: the number of syllables and the number of sentences in a text of 100 words. Reading ease is measured on a scale of 1 to 100, where a score of 30 is ‘very difficult’ and 70 is considered ‘easy’. A score of 100 indicates a text that can be read by a fourth grader, considered ‘functionally literate’ by the U.S. Census. A 0 to 30 score indicates a text that can be read only college graduate level readers.
The reading ease test achieves a score through the following formula:
In 1976, the U.S. Navy further modified the formula to produce a grade level score. Known as the Flesch-Kincaid formula, this readability test converts the 0-100 score to a U.S. grade level.
The Flesch-Kincaid formula is as follows:
The answer would give the grade level of the text. A score of 5.3 would mean that the document can be read by a student of the 5th grade. Theoretically, -3.01 would be the lowest score in this formula, but it would mean single -syllable words in every sentence.