ARI uses characters per word and words per sentence to produce a U.S. grade level for your text.
Use ARI when you need a fast, no-syllable readability check on technical text or live data streams. Its original purpose — grading Air Force training materials in real time — still makes it ideal for documentation, transcripts, and chat-log analysis.
ARI is essentially a faster cousin of Coleman–Liau. Both produce similar scores; ARI weights sentence length more, Coleman–Liau weights it less. Compared to Flesch–Kincaid, ARI is much more robust to vocabulary surprises.
The Automated Readability Index was developed in 1967 for the US Air Force as a fast readability check.
Like Coleman-Liau it relies on character counts, but it also factors in average sentence length directly.
ARI is particularly suitable for evaluating technical and instructional material.
Both rely on characters per word, but ARI also uses average sentence length while Coleman-Liau uses sentences per 100 words. They typically produce similar grade levels.
ARI was developed for the US Air Force in 1967, originally to grade training material.
Characters per word can be measured exactly by a computer, whereas syllable counting requires error-prone estimation. This makes ARI fully reproducible and well suited to automated tools.
ARI outputs a U.S. grade level, so a score of 8 corresponds to roughly an eighth-grade reading level. Lower scores indicate easier text and higher scores indicate more demanding writing.
Input
ARI uses characters per word and average sentence length to estimate a grade level.
Output
Automated Readability Index: 9.6 — 9th–10th grade.
Average 4.4 characters per word and 14 words per sentence. ARI adds the two with empirical weights to land on a US grade level near 10.
Classic 0–100 readability score.
readabilityU.S. grade level for your text.
readabilityPenalises complex (3+ syllable) words.
readabilityHealth & medical text grade level.