Free Readability Score Checker

What Is a Readability Score?

A readability score is a numerical estimate of how easy or difficult a piece of text is to read and understand, based on measurable factors like sentence length and word complexity (usually approximated by syllable count). Readability formulas were originally developed for educators to match reading materials to a student's grade level, but today they're widely used by content writers, UX designers, technical writers, and SEO professionals to make sure their writing is accessible to the intended audience.

This free tool calculates four of the most widely used readability formulas — Flesch-Kincaid Grade Level, Flesch Reading Ease, Gunning Fog Index, and SMOG Index — instantly and entirely in your browser, along with basic text statistics like word count, sentence count, and average sentence length.

What Each Index Measures

Flesch Reading Ease scores text on a 0-100 scale, where higher scores mean easier reading. It's calculated from average sentence length and average syllables per word. A score of 60-70 is considered easily understood by 13-15 year-olds (roughly 8th-9th grade); scores above 90 are very easy (5th grade level), while scores below 30 are very difficult, comparable to academic journal articles.

Flesch-Kincaid Grade Level uses the same underlying variables as Flesch Reading Ease but converts the result into a US school grade level. A score of 8.0 means the text is understandable by an average 8th grader. This formula is used by the U.S. Department of Defense and many government agencies to ensure documents are accessible to their intended audience.

Gunning Fog Index estimates the years of formal education a reader needs to understand the text on first read. It weighs "complex words" — those with three or more syllables — heavily, on the theory that long, unfamiliar words are the biggest barrier to comprehension. A Fog Index of 12 corresponds to a US high school senior reading level; most popular fiction sits between 8 and 12.

SMOG Index (Simple Measure of Gobbledygook) was designed specifically for evaluating health and safety materials, where comprehension accuracy matters more than speed. It focuses almost entirely on the number of polysyllabic (3+ syllable) words and is considered one of the more reliable formulas for predicting whether a reader will fully understand a text, not just skim it.

How to Use This Readability Checker

1. Paste or type your text into the box above — an article, essay, email, or web page copy.
2. Click Analyze.
3. Review the color-coded difficulty badge (Easy, Medium, or Hard) alongside the four index scores and text statistics.
4. Click Try Example to see how a dense, technical paragraph scores compared to plain, everyday writing.

Frequently Asked Questions

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