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Text diff checker
Compare two texts with a live line and word diff. Optional ignore-whitespace.
Readability checker
Paste your article, blog post, or documentation to analyze its readability and school grade level. The tool calculates Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog Index, Automated Readability Index (ARI), Coleman-Liau, and provides detailed metrics on words per sentence, syllable counts, and reading time.
Calculates client-side · Text never leaves your device
Flesch Reading Ease54.1 / 100
Fairly Difficult (10th–12th grade)
High school level. Typical of business reports and technical tutorials.
Flesch-Kincaid GradeGrade 9.1
9th Grade (High school)
US school grade level required to comfortably read this text on first pass.
Elementary (1–5)Middle (6–8)High (9–12)College (13+)
Additional Reading Formulas
Gunning Fog Index
11.3
Standard audience
Automated Readability (ARI)
11.2
Approx. grade 11
Coleman-Liau Index
13.3
Letter & sentence based index
Text Structure & Content Statistics
Words
95
Sentences
7
Syllables
156
Paragraphs
3
Words / Sentence
13.6
Syllables / Word
1.64
Complex Words (3+ syl)
14 (14.7%)
Characters (w/ spaces)
618
Characters (no spaces)
522
Est. Reading Time
~0.4 min
Est. Speaking Time
~0.7 min
Readability checker example
Standard blog post readability
A 300-word article with 15 words per sentence and 1.4 syllables per word scores ~68 on Flesch Reading Ease (Standard / Plain English, suited for an 8th-grade reading level), with an estimated reading time of 1.3 minutes.
Readability checker how-to
- Tokenize input text into sentences while protecting abbreviations (Mr., Dr., e.g., i.e.).
- Extract words, stripping punctuation while preserving hyphens and contractions.
- Count syllables per word using vowel group detection, handling silent trailing 'e' and 'ed' endings, and '-le' suffixes.
- Calculate average sentence length (words / sentences) and average syllables per word (syllables / words).
- Calculate Flesch Reading Ease = 206.835 - 1.015 * (words / sentences) - 84.6 * (syllables / words).
- Calculate Flesch-Kincaid Grade Level = 0.39 * (words / sentences) + 11.8 * (syllables / words) - 15.59.
- Identify complex words with 3 or more syllables to compute the Gunning Fog Index = 0.4 * ((words / sentences) + 100 * (complex words / words)).
- Compute Automated Readability Index (ARI) and Coleman-Liau Index, and estimate reading time at 225 wpm.
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Readability checker FAQ
- What is a readability checker?
- A readability checker estimates how easy a passage is to read, usually as an ease score and a US school grade level. This page runs Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, the Automated Readability Index (ARI), and Coleman-Liau. It runs in the browser, and the text is never uploaded.
- Does this readability checker send text to external APIs or LLMs?
- No. Readability scoring uses deterministic linguistic formulas running 100% in your browser. No text is sent to any server, third-party API, or AI model.
- What is a good Flesch Reading Ease score?
- For general web content, consumer products, and public guides, a score between 60 and 70 (Standard / Plain English) is recommended. Scores between 70 and 80 are easy to read (7th grade level). Scores below 50 reflect dense academic, technical, or legal prose.
- How does the Flesch-Kincaid Grade Level formula work?
- The formula is: 0.39 × (total words ÷ total sentences) + 11.8 × (total syllables ÷ total words) − 15.59. It indicates the number of years of formal education in the US school system typically required to understand the passage.
- What counts as a complex word in readability formulas?
- In the Gunning Fog Index and related metrics, words with three or more syllables (excluding common suffixes like -es, -ed, and -ing) are classified as complex or polysyllabic words.
- How do I calculate Flesch Reading Ease without this page?
- Tokenize text into words (regex /[^a-zA-Z0-9_-]+/) and sentences (split on [.!?]+ followed by whitespace, protecting common abbreviations like Mr. and Dr.). For each word, count syllables by matching vowel clusters [aeiouy]+, deducting silent trailing 'e' and non-t/d 'ed' endings, and adding 1 for consonant+'-le' endings (minimum 1 syllable per word). Compute avgWordsPerSentence = words / sentences and avgSyllablesPerWord = syllables / words. Flesch Reading Ease = 206.835 - 1.015 * avgWordsPerSentence - 84.6 * avgSyllablesPerWord. Clamp score to 0..100. Flesch-Kincaid Grade = 0.39 * avgWordsPerSentence + 11.8 * avgSyllablesPerWord - 15.59.
- How much text is needed for an accurate readability score?
- Readability formulas rely on statistical averages of sentence lengths and syllable counts. While Plaintools analyzes passages of any length, a sample of at least 100 to 200 words delivers reliable, representative scores without single-sentence skew.