Automated readability index (ARI) calculator
ARI estimates the US grade level needed to understand English text and is often used to review manuals and technical instructions.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter text.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
ARI = 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43, where characters are Latin letters and digits, excluding spaces and punctuation.
Example
Result: ARI score: 13.47; Characters per word: 6.67; Words per sentence: 7.
Limits and caveats
- English only; non-Latin words are ignored.
- Abbreviations ending in a full stop may add sentences and lower the score.
Questions about this tool
How do I turn the score into a grade?
Round the score up, so 7.2 corresponds to roughly US 8th grade.
Why does ARI count characters?
It was designed to be computed mechanically, and counting characters is more exact than estimating syllables.
Can the score be negative?
Yes. Very short sentences with short words can score below zero, which means very easy text.