Enter the average sentence length and the average number of syllables per word into the calculator to determine the Flesch Reading Ease score. This calculator can also evaluate any of the variables given the others are known.

Flesch Index Formula

The following formula is used to calculate the Flesch Reading Ease score (FRES).

FRES = 206.835 - (1.015 * ASL) - (84.6 * ASW)

Variables:

• FRES is the Flesch Reading Ease score
• ASL is the average sentence length (the number of words divided by the number of sentences)
• ASW is the average number of syllables per word (the number of syllables divided by the number of words)

To calculate the Flesch Reading Ease score, first calculate the average sentence length and the average number of syllables per word. Then, multiply the average sentence length by 1.015 and the average number of syllables per word by 84.6. Subtract these two results from 206.835 to get the Flesch Reading Ease score.

What is a Flesch Index?

The Flesch Index, also known as the Flesch Reading Ease Score, is a tool used to assess the readability of an English text. It uses a mathematical formula to calculate a score based on the average number of syllables per word and the average number of words per sentence. The resulting score ranges from 0 to 100, with a higher score indicating easier readability. This index is commonly used in the fields of education and journalism to ensure written materials are appropriate for the intended audience’s reading ability.

How to Calculate Flesch Index?

The following steps outline how to calculate the Flesch Index:

1. First, determine the average sentence length (ASL) by dividing the number of words by the number of sentences.
2. Next, determine the average number of syllables per word (ASW) by dividing the number of syllables by the number of words.
3. Next, gather the formula from above: FRES = 206.835 – (1.015 * ASL) – (84.6 * ASW).
4. Finally, calculate the Flesch Index using the formula.
5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge:

ASL (average sentence length) = 15

ASW (average number of syllables per word) = 2.5