About ReadabilityTool
A free, simple tool for measuring how easy your writing is to read.
What Is ReadabilityTool?
ReadabilityTool is a free online tool that instantly analyzes the readability of any text. Paste your writing into the tool and within seconds you'll see six different readability scores, a word and sentence breakdown, and plain-language observations about your text's complexity.
There's no account required, no software to install, and no cost. ReadabilityTool works entirely in your browser — your text is never sent to any server or stored anywhere.
Why Readability Matters
Clear writing is one of the most valuable skills in any field. Research consistently shows that simpler, more readable text leads to better comprehension, higher engagement, and more trust from readers — whether you're writing a blog post, a patient education brochure, a legal document, or a school assignment.
Readability formulas give you an objective way to measure how accessible your writing is. Rather than guessing whether your text is too complex, you can see a specific score and make targeted improvements.
Who Is It For?
Bloggers & Content Writers
Check that your articles are accessible to a general audience. Most web content performs best at a 6th–8th grade reading level.
Students & Educators
Students can check essays and assignments for clarity. Teachers can evaluate whether reading materials match their students' level.
Healthcare Professionals
Patient education materials should target a 6th grade reading level or below. The SMOG Index is the standard formula for health communications.
Legal & Business Writers
Contracts, policies, and business documents are often far more complex than necessary. Readability scores help identify where plain language improvements can be made.
SEO & Marketing Professionals
Search engines favor content that matches the reading level of its target audience. Readability is one factor in producing content that ranks and converts.
Technical Writers
Technical documentation needs to be precise without being unnecessarily complex. Tools like the Coleman-Liau Index and ARI are well-suited for technical text.
How to Use ReadabilityTool
Copy any text — an article, essay, email, document, or anything you've written — and paste it into the text box on the main tool page.
Hit the Analyze Text button and the tool instantly calculates all six readability scores along with word count, sentence count, average sentence length, and estimated reading time.
Each score card shows your result with a plain-language label. The Breakdown panel below gives you specific observations about sentence length and vocabulary complexity.
The Six Readability Formulas
Flesch Reading Ease
Developed by Rudolf Flesch in 1948, this formula rates text on a scale from 0 to 100. Higher scores indicate easier reading. A score of 60–70 is considered standard for general audiences. The formula is based on average sentence length and average syllables per word. It is widely used by U.S. government agencies, publishers, and content writers.
Flesch-Kincaid Grade Level
Developed for the U.S. Navy in 1975, the Flesch-Kincaid Grade Level formula converts the Flesch Reading Ease calculation into a U.S. school grade level. A score of 8 means an 8th grader can comfortably read the text. It uses the same variables — sentence length and syllables per word — but outputs a grade level rather than a 0–100 score.
Gunning Fog Index
Created by Robert Gunning in 1952, the Fog Index estimates the years of formal education needed to understand a piece of writing. It places particular weight on "complex words" — defined as words with three or more syllables. A score of 12 corresponds to a high school graduate. Most business writing guidelines recommend keeping the Fog Index below 12.
SMOG Index
SMOG stands for Simple Measure of Gobbledygook. Developed by G. Harry McLaughlin in 1969, it estimates grade level based entirely on the count of polysyllabic words (3+ syllables). It requires a minimum of 30 sentences for accuracy and is the standard readability formula used in healthcare, public health communications, and patient education materials.
Coleman-Liau Index
Developed in 1975 by Meri Coleman and T. L. Liau, this formula differs from most others by using characters per word rather than syllable counts. This makes it more consistent for technical writing, scientific papers, and texts with unusual vocabulary. It returns a U.S. grade level estimate.
Automated Readability Index (ARI)
Introduced in 1967, the ARI was designed to be calculated by machines — one of the first readability formulas built for automated analysis. It uses characters per word and words per sentence to estimate grade level. Originally developed for U.S. Air Force technical manuals, it remains widely used for technical and government writing assessment.
Privacy
ReadabilityTool processes all text entirely within your browser using JavaScript. Your text is never sent to any server, never stored, and never shared with any third party. When you close or refresh the page, your text is gone. We do not collect any personally identifiable information.
Free to Use
ReadabilityTool is completely free to use with no account, no subscription, and no limits on how much text you can analyze. All six readability formulas are available on every visit at no cost.