Automated page. Written and translated automatically by AI and checked against the sources by software; no human editor. SI-IQ is an index built from public benchmark results, not an IQ test. How it works
Claude Sonnet 5.5 vs GPT-6 Astra: which is smarter?
Claude Sonnet 5.5 has an SI-IQ of 140 and GPT-6 Astra has 150. The table compares them area by area using only independent benchmark results.
| Metric | Claude Sonnet 5.5 | GPT-6 Astra |
|---|---|---|
| SI-IQ | 140137–143 | 150146–153 |
| Reasoning | 142 | 154 |
| Math | 140 | 148 |
| Knowledge | 137 | 149 |
| Developer | Anthropic | OpenAI |
| Released | Sep 28, 2026 | Sep 3, 2026 |
| Access | API access | API access |
| Price in / out (USD per 1M tokens) | $2.00 / $10 | $10 / $50 |
| Benchmarks used | 8 | 8 |
Claude Sonnet 5.5GPT-6 Astra
Benchmarks every compared model was tested on
Raw scores as published by the evaluators.
| Benchmark | Claude Sonnet 5.5 | GPT-6 Astra |
|---|---|---|
| Chess Puzzles | 59.0% | 74.0% |
| FrontierMath Tier 4 | 80.5% | 97.6% |
| FrontierMath Tiers 1–3 | 88.8% | 93.7% |
| Furniture Assembly | 75.0% | 80.0% |
| GPQA Diamond | 95.6% | 95.8% |
| GPQA Diamond (OpenRouter run) | 92.9% | 94.7% |
| Mystery Game Puzzles | 65.0% | 84.0% |
| OTIS Mock AIME 2024–2025 | 100.0% | 100.0% |
| SimpleQA Verified | 46.5% | 75.6% |
| τ²-bench Airline (OpenRouter run) | 77.5% | 67.7% |
On SI-IQ, GPT-6 Astra is ahead by 9 points, and the 90% intervals do not overlap.
Data sources: Epoch AI, ‘Capabilities & benchmarking’ (CC BY 4.0); API list prices via LiteLLM's price table (MIT); each price links to the developer's pricing page; Source: OpenRouter (openrouter.ai), licensed under CC BY 4.0: reuse and republish with attribution to OpenRouter..