Score text readability with Flesch-Kincaid, Gunning Fog, Coleman-Liau, SMOG, and ARI. Get grade-level estimates and improvement tips in your browser.
Readability Analyzer processes your text in the browser, which means even sensitive strings stay private.
It's one of the free
String & Text Tools
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Use it below, then scroll down for a step-by-step guide, answers to common questions, and related tools.
About Readability Analyzer
The Readability Analyzer evaluates how easy your text is to read using five established readability formulas used by educators, publishers, and content strategists worldwide. Each formula approaches readability from a different angle — some count syllables, others measure word length or sentence complexity — giving you a comprehensive, multi-dimensional view of your content's reading difficulty. All analysis runs instantly in your browser with no data transmitted to any server.
Understanding the readability scores
The Flesch-Kincaid Reading Ease score ranges from 0-100, where higher scores mean easier reading (60-70 is ideal for web content). The Flesch-Kincaid Grade Level maps text to a US school grade (e.g., 8.0 means an 8th grader can understand it). The Gunning Fog Index estimates years of formal education needed. The Coleman-Liau Index uses character counts instead of syllables, making it more consistent across different word types. The SMOG Index focuses on polysyllabic words and is considered the most reliable for healthcare and technical content. The Automated Readability Index (ARI) uses characters per word and words per sentence for a character-based grade estimate.
Why readability matters for SEO and engagement
Google's Search Quality Guidelines emphasize content that is easy to understand and provides clear value to users. While readability score itself is not a direct ranking factor, its effects are: content written at appropriate reading levels receives longer dwell times, lower bounce rates, and higher engagement — all of which are user experience signals that search engines measure. Studies show that lowering content from a 12th-grade to an 8th-grade reading level can increase engagement by 40-60% for general audiences.
What is the Readability Analyzer?
The Readability Analyzer is a comprehensive tool designed to evaluate the complexity, tone, and readability of your text. It instantly calculates industry-standard metrics like the Flesch-Kincaid Grade Level, Gunning Fog Index, and Coleman-Liau Index, while also leveraging AI heuristics to provide actionable suggestions for improving sentence structure. Because it runs 100% locally in your browser, it is the perfect privacy-focused solution for analyzing confidential company memos, unreleased blog posts, or sensitive client emails without risking data leaks.
How does it work?
The tool uses client-side JavaScript to parse your text, counting syllables, words, and sentences using precise linguistic algorithms. It then plugs these values into established readability formulas. Additionally, it uses a lightweight, browser-based NLP pipeline to flag passive voice, overly complex words, and run-on sentences. All of this parsing and mathematical calculation happens within milliseconds on your own CPU, ensuring immediate feedback with zero server latency.
Common use cases
Technical writers use the Readability Analyzer to ensure their software documentation is accessible to junior developers (aiming for an 8th-grade reading level). Copywriters use it to optimize landing page copy, ensuring the text is punchy, easily digestible, and devoid of confusing jargon. HR professionals use it to simplify employee handbooks and policy documents so they can be easily understood by the entire workforce.
It’s easy to be overwhelmed by five scores, but they’re mostly variations on a theme — they all reward shorter sentences and simpler words, just weighted differently:
| Formula | Counts | Best for |
|---|
| Flesch Reading Ease | Syllables + sentence length | Quick 0–100 gut check (higher = easier) |
| Flesch–Kincaid Grade | Syllables + sentence length | US grade-level target |
| Gunning Fog | ”Complex” words + sentence length | Business / technical writing |
| SMOG | Polysyllable density | Health and safety content (conservative) |
| Coleman–Liau / ARI | Characters (not syllables) | Automated pipelines (no syllable guessing) |
When they disagree, trust the character-based scores (Coleman–Liau, ARI) for automated reliability and Flesch–Kincaid for the number most editors and style guides expect.
What “good” looks like by audience
- General web / news: 7th–8th grade (Flesch Reading Ease 60–70). This is where most successful blogs and marketing copy land.
- Email and landing pages: aim even lower — 6th grade keeps conversion-critical copy frictionless.
- Technical docs: 10th–12th grade is acceptable when the audience is specialists, but never let jargon inflate it needlessly.
The principle behind every target: write at or below your reader’s level. Writing up to impress almost always costs you comprehension.
Why syllable counting is a heuristic, not gospel
English pronunciation is famously irregular (“queue” is one syllable, “area” is three), so any syllable-based formula uses a vowel-group heuristic with patches for silent-e, -le endings, and common prefixes. On a single odd word it can be off by one; across a full passage those errors average out, which is exactly how the formulas were designed to be used. Don’t over-read a one-point swing — look at the trend after an edit, not the third decimal place.
A workflow that compounds
Analyze, fix the three longest sentences, then re-analyze. That single loop, repeated twice, does more for clarity than any amount of word-by-word tinkering — because long sentences are where readers actually lose the thread.
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