Claude Opus 4.5 Pro vs GPT-5.1 Max: which model should you choose?
We compared Claude Opus 4.5 Pro and GPT-5.1 Max on price, context window and 12 benchmarks. Claude Opus 4.5 Pro has the stronger average benchmark score; Claude Opus 4.5 Pro is cheaper on a blended 3:1 basis.
Claude Opus 4.5 Pro
Claude Opus 4.5 Pro is a frontier model from Anthropic. It offers a 200,000-token context window, costs $20.98 per million input tokens and $85.59 per million output tokens, and averages 89.1 across the index's benchmark suite.
- Input
- $20.98 / 1M
- Output
- $85.59 / 1M
- Context
- 200,000
- Avg score
- 89.1
- 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 Pro | GPT-5.1 Max | Edge |
|---|---|---|---|
| Input price / 1M | $20.98 | $20.50 | B |
| Output price / 1M | $85.59 | $103.98 | A |
| Context window | 200,000 | 2,000,000 | B |
| Max output | 32,768 | 8,192 | A |
| Average score | 89.1 | 87.9 | A |
| Arena Elo | 1483.9 | 1478.2 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Opus 4.5 Pro wins 7, GPT-5.1 Max wins 5, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Opus 4.5 Pro | GPT-5.1 Max | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 91.2 | 91.3 | 0.1 | GPT-5.1 Max |
| GPQA Diamond | 86.0 | 86.4 | 0.4 | GPT-5.1 Max |
| SWE-bench Verified | 81.1 | 75.6 | 5.5 | Claude Opus 4.5 Pro |
| HumanEval | 93.4 | 92.2 | 1.2 | Claude Opus 4.5 Pro |
| MATH-500 | 91.2 | 91.3 | 0.1 | GPT-5.1 Max |
| AIME 2025 | 91.4 | 88.8 | 2.6 | Claude Opus 4.5 Pro |
| LiveCodeBench | 84.1 | 80.2 | 3.9 | Claude Opus 4.5 Pro |
| IFEval | 96.1 | 92.2 | 3.9 | Claude Opus 4.5 Pro |
| TruthfulQA | 86.7 | 91.1 | 4.4 | GPT-5.1 Max |
| HellaSwag | 95.2 | 93.1 | 2.1 | Claude Opus 4.5 Pro |
| MMMU | 83.3 | 85.1 | 1.8 | GPT-5.1 Max |
| Arena Elo | 1483.9 | 1478.2 | 5.7 | Claude Opus 4.5 Pro |
Price analysis
On a blended 3:1 input-to-output basis, Claude Opus 4.5 Pro costs about $37.13 per million tokens and GPT-5.1 Max costs about $41.37. Claude Opus 4.5 Pro is roughly 10% cheaper than GPT-5.1 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 200,000 for Claude Opus 4.5 Pro. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Opus 4.5 Pro wins 7, GPT-5.1 Max wins 5, and 0 are tied. On the index average, Claude Opus 4.5 Pro leads GPT-5.1 Max by 1.2 points (89.1 versus 87.9).
The price picture favours Claude Opus 4.5 Pro. 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 Claude Opus 4.5 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Opus 4.5 Pro 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 32,768-token output limit.
Choose GPT-5.1 Max if
- You need the larger 2,000,000-token context window.
FAQ
Is Claude Opus 4.5 Pro better than GPT-5.1 Max?
On the index average, Claude Opus 4.5 Pro leads GPT-5.1 Max by 1.2 points (89.1 versus 87.9). The better choice depends on price, context and your task. Claude Opus 4.5 Pro wins 7 benchmarks, GPT-5.1 Max wins 5.
Which is cheaper, Claude Opus 4.5 Pro or GPT-5.1 Max?
Claude Opus 4.5 Pro is cheaper on a blended 3:1 basis at about $37.13 per million tokens, versus $41.37 for GPT-5.1 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 Pro has 200,000 tokens.
Are these models open weights?
Claude Opus 4.5 Pro is proprietary; GPT-5.1 Max is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Opus 4.5 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.