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Claude Opus 5.5 vs GPT-6 Astra: which is smarter?
Claude Opus 5.5 has an SI-IQ of 144 and GPT-6 Astra has 150. The table compares them area by area using only independent benchmark results.
Data as of Oct 18, 2026 · method 1.0.0
| Metric | Claude Opus 5.5 | GPT-6 Astra |
|---|---|---|
| SI-IQ | 144141–148 | 150146–153 |
| Reasoning | 146 | 154 |
| Math | 145 | 148 |
| Knowledge | 137 | 149 |
| Developer | Anthropic | OpenAI |
| Released | Sep 22, 2026 | Sep 3, 2026 |
| Access | API access | API access |
| Price in / out (USD per 1M tokens) | $4.00 / $20 | $10 / $50 |
| Benchmarks used | 9 | 9 |
The difference of 5 points is within the statistical uncertainty: the two models are roughly on par.
Data sources: Arena leaderboard dataset on Hugging Face (CC BY 4.0); Epoch AI, ‘Capabilities & benchmarking’ (CC BY 4.0); LiteLLM, model_prices_and_context_window.json (MIT); Source: OpenRouter (openrouter.ai), licensed under CC BY 4.0: reuse and republish with attribution to OpenRouter (licences and changes).