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Automated Readability Index (ARI) Calculator

Calculate the ARI of any text from characters, words and sentences, mapped to US grade level and reader age. Free, instant, 100% in-browser.

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ARI score
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Characters (A–Z, 0–9)
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Words
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Sentences

What is the Automated Readability Index (ARI) Calculator?

The Automated Readability Index (ARI) estimates the US grade level — and reader age — needed to understand your text.

  • Standard ARI formula with correct round-up to the next level
  • Full 14-level table mapping score to US grade and reader age
  • Character, word and sentence counts shown
  • Character-based — no syllable estimation error
  • Live recalculation as you edit
  • Runs entirely offline in your browser

How to use the Automated Readability Index (ARI) Calculator

  1. 1

    Paste your text into the input box.

  2. 2

    Read the raw ARI score and the rounded-up level.

  3. 3

    Find your highlighted row in the grade and reader-age table.

  4. 4

    Shorten sentences or words and watch the score update live.

About the Automated Readability Index (ARI) Calculator

The Automated Readability Index (ARI) estimates the US grade level — and reader age — needed to understand your text. This calculator applies the standard formula, 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43, rounds the result up as ARI specifies, and highlights your level in the full 14-row grade and age table.

Like Coleman–Liau, ARI is character-based: it counts letters and digits rather than estimating syllables, which is why it was one of the first formulas run automatically — it was developed in 1967 for military typewriter output. Writers use it alongside syllable-based scores to separate a long-word problem from a long-sentence problem.

Everything is computed 100% locally in your browser. Your text is never uploaded, and the tool works offline once loaded.

Frequently asked questions

How is the Automated Readability Index calculated?

ARI = 4.71 × (characters ÷ words) + 0.5 × (words ÷ sentences) − 21.43, where characters are letters and digits only. The result is rounded up to the next whole number, and that level maps to a US grade: 1 is kindergarten, 8 is seventh grade, 14 is college.

What do the ARI levels mean?

Each level corresponds to a US school grade and typical reader age — level 1 is ages 5–6 (kindergarten), level 9 is ages 13–14 (eighth grade), and level 14 is college, ages 18–22. The table on this page shows all fourteen levels with your text's row highlighted.

Why does ARI round up instead of to the nearest number?

The index is defined conservatively: a raw score of 8.1 means eighth-grade text is not quite enough, so it reports level 9. This tool follows that original convention rather than ordinary rounding.

How is ARI different from Flesch-Kincaid?

Both output a grade level, but ARI measures word difficulty in characters per word while Flesch–Kincaid uses syllables per word. ARI needs no pronunciation guessing, so its inputs are exact; Flesch–Kincaid tracks spoken difficulty slightly better. They usually agree within a grade or two.

Is my text sent to a server?

No. Counting and scoring happen in your browser with JavaScript. Your text never leaves your device.

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