Automated Readability Index calculator
Grade 8 or lower for general audiences. ARI tends to run slightly higher than Flesch–Kincaid on text with long technical words.
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Automated Readability Index
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Formula: 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43
- Words
- 0
- Sentences
- 1
- Letters and digits
- 0
How to read the ARI score
| Score | Meaning |
|---|---|
| 5 or below | Very easy: understood by most 10–11 year olds |
| 6–8 | Plain English: the target for email, web copy and public information |
| 9–10 | Fairly difficult: fine for engaged professional readers |
| 11–12 | Difficult: typical of specialist reports |
| 13–16 | College level: academic and technical writing |
| 17+ | Graduate level: legal and scientific text |
Lower scores mean easier text.
Where the Automated Readability Index comes from
Developed by E. A. Smith and R. J. Senter in 1967 for the US Air Force, designed to be computed in real time by electric typewriters counting keystrokes.
Other readability formulas
- Flesch–Kincaid Grade Level: 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59
- Flesch Reading Ease: 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)
- Gunning Fog Index: 0.4 × [(words ÷ sentences) + 100 × (complex words ÷ words)]
- SMOG Index: 1.043 × √(polysyllables × 30 ÷ sentences) + 3.1291
- Coleman–Liau Index: 0.0588 × L − 0.296 × S − 15.8 (L = letters per 100 words, S = sentences per 100 words)
Questions people ask
What does the ARI score mean?
It approximates the US school grade needed to understand the text: 8 means an eighth grader, 12 a high-school senior.
What counts as a character in ARI?
Letters and digits in words, not spaces or punctuation.