Claude Opus 4.5 Max vs GPT-5.1 Max: which model should you choose?
We compared Claude Opus 4.5 Max and GPT-5.1 Max on price, context window and 12 benchmarks. GPT-5.1 Max has the stronger average benchmark score; GPT-5.1 Max is cheaper on a blended 3:1 basis.
Claude Opus 4.5 Max
Claude Opus 4.5 Max is a frontier model from Anthropic. It offers a 1,000,000-token context window, costs $20.90 per million input tokens and $106.51 per million output tokens, and averages 87.8 across the index's benchmark suite.
- Input
- $20.90 / 1M
- Output
- $106.51 / 1M
- Context
- 1,000,000
- Avg score
- 87.8
- Open weights
- No
GPT-5.1 Max
GPT-5.1 Max is a frontier model from OpenAI. It offers a 2,000,000-token context window, costs $20.50 per million input tokens and $103.98 per million output tokens, and averages 87.9 across the index's benchmark suite.
- Input
- $20.50 / 1M
- Output
- $103.98 / 1M
- Context
- 2,000,000
- Avg score
- 87.9
- Open weights
- No
Specification comparison
| Spec | Claude Opus 4.5 Max | GPT-5.1 Max | Edge |
|---|---|---|---|
| Input price / 1M | $20.90 | $20.50 | B |
| Output price / 1M | $106.51 | $103.98 | B |
| Context window | 1,000,000 | 2,000,000 | B |
| Max output | 16,384 | 8,192 | A |
| Average score | 87.8 | 87.9 | B |
| Arena Elo | 1501.9 | 1478.2 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Opus 4.5 Max wins 6, GPT-5.1 Max wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Opus 4.5 Max | GPT-5.1 Max | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 89.5 | 91.3 | 1.8 | GPT-5.1 Max |
| GPQA Diamond | 84.6 | 86.4 | 1.8 | GPT-5.1 Max |
| SWE-bench Verified | 79.5 | 75.6 | 3.9 | Claude Opus 4.5 Max |
| HumanEval | 91.7 | 92.2 | 0.5 | GPT-5.1 Max |
| MATH-500 | 94.2 | 91.3 | 2.9 | Claude Opus 4.5 Max |
| AIME 2025 | 89.3 | 88.8 | 0.5 | Claude Opus 4.5 Max |
| LiveCodeBench | 80.6 | 80.2 | 0.4 | Claude Opus 4.5 Max |
| IFEval | 94.5 | 92.2 | 2.3 | Claude Opus 4.5 Max |
| TruthfulQA | 86.9 | 91.1 | 4.2 | GPT-5.1 Max |
| HellaSwag | 93.0 | 93.1 | 0.1 | GPT-5.1 Max |
| MMMU | 82.3 | 85.1 | 2.8 | GPT-5.1 Max |
| Arena Elo | 1501.9 | 1478.2 | 23.7 | Claude Opus 4.5 Max |
Price analysis
On a blended 3:1 input-to-output basis, Claude Opus 4.5 Max costs about $42.30 per million tokens and GPT-5.1 Max costs about $41.37. GPT-5.1 Max is roughly 2% cheaper than Claude Opus 4.5 Max. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
GPT-5.1 Max has the larger context window at 2,000,000 tokens, compared with 1,000,000 for Claude Opus 4.5 Max. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Opus 4.5 Max wins 6, GPT-5.1 Max wins 6, and 0 are tied. On the index average, GPT-5.1 Max leads Claude Opus 4.5 Max by 0.1 points (87.9 versus 87.8).
The price picture favours GPT-5.1 Max. The context picture favours GPT-5.1 Max. Those two dimensions often matter more than a few benchmark points once a model is good enough for the task.
If you need a single default, start with GPT-5.1 Max for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Opus 4.5 Max if
- You need the larger 16,384-token output limit.
Choose GPT-5.1 Max if
- You want the higher average benchmark score in this index.
- Unit cost matters and you want the cheaper blended price.
- You need the larger 2,000,000-token context window.
FAQ
Is Claude Opus 4.5 Max better than GPT-5.1 Max?
On the index average, GPT-5.1 Max leads Claude Opus 4.5 Max by 0.1 points (87.9 versus 87.8). The better choice depends on price, context and your task. Claude Opus 4.5 Max wins 6 benchmarks, GPT-5.1 Max wins 6.
Which is cheaper, Claude Opus 4.5 Max or GPT-5.1 Max?
GPT-5.1 Max is cheaper on a blended 3:1 basis at about $41.37 per million tokens, versus $42.30 for Claude Opus 4.5 Max.
Which has the larger context window?
GPT-5.1 Max has the larger context window at 2,000,000 tokens. Claude Opus 4.5 Max has 1,000,000 tokens.
Are these models open weights?
Claude Opus 4.5 Max is proprietary; GPT-5.1 Max is proprietary.
Which should I choose for production?
If you need a single default, start with GPT-5.1 Max for quality-sensitive work, and check whether its price holds at your expected volume before committing.