Readability Calculators

Magnifying glass over documents

Readability calculators take a sample of your writing and calculate the number of sentences, words, syllables, and characters. They are helpful when deciding if your writing is at the appropriate level for your intended audience. Below are a selection of commonly used readability calculators when assessing health literacy levels. 

The Flesch Grade Level Readability Formula

The formula is used in business, industry and government as well as education, to score materials from the upper elementary level through the secondary grades and beyond. The formula takes into consideration (1) the total number of words, and (2) the number syllables, and (3) the total number of sentences. It is one of the most popular and heavily tested formulas.

Fry Graph Reading Formula

Calculates reading difficulty level by the average number of sentences and syllables per hundred words. These averages are plotted onto a specific graph; the intersection of the average number of sentences and the average number of syllables determines the reading level of the content.

Gunning Fog Index

Estimates the years of formal education a person needs to understand the text on the first reading. For instance, a fog index of 12 requires the reading level of a United States high school senior (around 18 years old).

New Dale-Chall Readability Formula

Calculates the US grade level of a text sample based on sentence length and the number of ‘hard’ words. These ‘hard’ words are words that do not appear on a specially designed list of common words familiar to most 4th-grade students.

SMOG – Simple Measure of Gobbledygook

Measures readability that estimates the years of education needed to understand a piece of writing.



Last modified: 09/02/21