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Epoch Capabilities Index (ECI)

The Epoch Capabilities Index is Epoch AI's composite score of model capability, estimated from results across many benchmarks with a statistical model so that models can be placed on one scale.

Because it combines many benchmarks, ECI is less sensitive to any single test. It comes with a confidence interval, shown on each model page. New models receive a score only after Epoch AI has evaluated them.

Related ranking: LLM leaderboard

  1. 1.Claude Opus 5.5 Anthropic167.3
  2. 2.GPT-6 Astra OpenAI166.5
  3. 3.Claude Sonnet 5.5 Anthropic165.2
  4. 4.Claude Fable 5.1 Anthropic164.8
  5. 5.Claude Opus 5 Anthropic162.9

Ranked by the Epoch Capabilities Index (ECI) - Epoch AI's statistical model over dozens of benchmarks. Source: Epoch AI. Full ranking

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Explanation written by AI Stats Live editors; last reviewed 29 Sep 2026. Examples and rankings update automatically from the sources listed on the methodology page.