Supports plain text — minimum 30 sentences recommended for SMOG accuracy
Readability scores appear here
Paste text and click Analyze to score across 4 indexes// score text readability across 4 proven indexes
Analyze text readability with Flesch-Kincaid, Gunning Fog, SMOG, and Coleman-Liau indexes. Free browser-based tool with instant scoring.
Readability scores appear here
Paste text and click Analyze to score across 4 indexesCopy and paste any text — articles, essays, reports, emails, or documentation into the input area.
Hit the Analyze button (or Ctrl+Enter) to instantly compute all four readability scores.
Review the grade levels and ease scores. Lower grade = broader audience. Aim for grade 8 for general public content.
This tool scores your text using four established readability formulas. Each uses a different approach — syllable counting, word length, sentence length, and complex word ratios — giving you a comprehensive picture of how accessible your writing is to readers of different education levels.
The Flesch Reading Ease formula scores text on a 0–100 scale. Higher scores indicate material that is easier to read. A score of 60–70 is considered standard for general audiences. Scores below 30 are very difficult, while scores above 90 are very easy to read.
The Gunning Fog Index estimates the years of formal education required to understand a piece of text on first reading. A score of 8 is ideal for most public-facing content. The formula penalizes long sentences and words with three or more syllables (complex words).
The SMOG (Simple Measure of Gobbledygook) formula was designed for documents with at least 30 sentences. With fewer sentences, the sample size is too small for accurate polysyllabic word counting, so scores may be less reliable. The tool will warn you when your text is below this threshold.
Unlike the Flesch-Kincaid and Gunning Fog formulas, Coleman-Liau does not use syllable counts at all. Instead, it measures the average number of letters per 100 words and sentences per 100 words. This makes it easier to compute programmatically and generally correlates well with the other indexes.
For general public content — blogs, news, emails — aim for a Flesch-Kincaid Grade Level of 6–8, which corresponds to middle school reading ability. Academic writing typically sits at Grade 12–16. If you're writing for a broad audience, keep sentences short and prefer common shorter words.
Yes — the text is sent to the server for analysis via a lightweight API request. No text is stored, logged, or retained after the analysis is complete. The calculation happens server-side and only the scores are returned to your browser.
All four readability formulas were developed and validated specifically for English text. Results for other languages will be mathematically computed but will not be meaningful, as syllable patterns, word lengths, and sentence structures differ significantly between languages.
For meaningful results, use at least 100–200 words. Very short snippets of 20–30 words may produce skewed scores since readability formulas rely on statistical averages across multiple sentences and words. Longer samples provide more reliable and stable scores across all four indexes.
A text readability analyzer is a tool that measures how easy or difficult a piece of writing is to understand. By applying mathematical formulas developed by researchers in linguistics and education, it assigns a numerical score — often expressed as a grade level — that tells you what level of education a reader typically needs to comprehend your text comfortably.
Readability scores are widely used by content writers, educators, UX writers, medical communicators, legal professionals, and SEO specialists to ensure their writing is appropriate for their target audience. Writing that's too complex loses readers; writing that's too simple can undermine credibility in professional or academic contexts.
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This tool calculates four of the most widely trusted and cited readability indexes, each using a slightly different approach to measuring text complexity.
Developed by Rudolf Flesch in 1948 and later adapted by J. Peter Kincaid for the U.S. Navy, these two related formulas are the most widely used readability measures in the world. The Flesch Reading Ease score ranges from 0 to 100 — higher is easier. It's calculated based on average sentence length and average number of syllables per word.
The Flesch-Kincaid Grade Level converts the same inputs into a U.S. school grade level. A score of 8.0 means an 8th grader should be able to understand the text. Most popular newspapers and general audience content targets a score of 6–10. The U.S. Department of Defense even mandates FK Grade Level assessments for certain official documents.
Created by Robert Gunning in 1952, the Gunning Fog Index focuses heavily on "complex words" — words with three or more syllables. The formula estimates the years of formal education a reader needs to understand text on first reading. A score of 12 corresponds to a high school senior; a score of 17 corresponds to a college graduate.
The Fog Index is particularly popular in journalism and business writing. Time magazine typically scores around 11, while The Harvard Law Review often scores above 20. Writers aiming for broad audiences should target a Fog Index below 12.
SMOG stands for Simple Measure of Gobbledygook. Developed by G. Harry McLaughlin in 1969, the SMOG Index is widely used in healthcare communication, where reading level directly impacts patient outcomes. The formula counts polysyllabic words (3+ syllables) across 30 sentences.
SMOG is considered highly accurate for predicting comprehension difficulty, particularly for health literacy assessments. The U.S. National Institutes of Health recommends that patient education materials score at or below a SMOG Grade of 6–8. Because SMOG relies on 30-sentence samples, shorter texts will produce approximate estimates only.
Meri Coleman and T. L. Liau introduced this formula in 1975 as an alternative to syllable-counting methods, which can be difficult to automate reliably. Instead, Coleman-Liau uses the number of letters per 100 words and the number of sentences per 100 words — both of which are easy to count programmatically and produce results comparable to the Flesch-Kincaid Grade Level.
The Coleman-Liau Index is popular in natural language processing and computational linguistics precisely because character counts are far simpler to compute than syllable counts, especially for automated large-scale text analysis.
Knowing your readability score is only the first step. Here's how to act on the results:
Here's a quick reference for interpreting grade-level scores across all four indexes:
Readability scoring is used across a remarkably wide range of industries. Content marketers use it to ensure blog posts and landing pages reach their intended audience. SEO specialists track it as a quality signal, since Google's quality guidelines implicitly favor clear, accessible content. Healthcare writers rely heavily on SMOG to keep patient materials at an appropriate literacy level. Legal teams use it to assess contract clarity. UX writers run readability checks on error messages, onboarding flows, and UI copy to ensure clarity under pressure.
Academic researchers also use readability formulas to study text corpora, compare writing styles across time periods, and evaluate educational materials for age-appropriateness.
While powerful, readability scores are not a complete picture of writing quality. They measure structural complexity — sentence length, word length, syllable counts — but do not measure clarity of thought, logical flow, vocabulary appropriateness, or cultural accessibility. A sentence can be structurally simple but confusing due to poor organization or ambiguous pronouns.
Additionally, all four formulas were designed and validated for English. Results for other languages may be computed but should not be interpreted as meaningful grade-level assessments. Use readability scores as one diagnostic tool among many, not as the sole measure of writing quality.