Claude Sonnet 4.5 Max vs GPT-5.1 Max: which model should you choose?
We compared Claude Sonnet 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; Claude Sonnet 4.5 Max is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Max
Claude Sonnet 4.5 Max is a frontier model from Anthropic. It offers a 1,000,000-token context window, costs $19.90 per million input tokens and $95.47 per million output tokens, and averages 87.2 across the index's benchmark suite.
- Input
- $19.90 / 1M
- Output
- $95.47 / 1M
- Context
- 1,000,000
- Avg score
- 87.2
- 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 Sonnet 4.5 Max | GPT-5.1 Max | Edge |
|---|---|---|---|
| Input price / 1M | $19.90 | $20.50 | A |
| Output price / 1M | $95.47 | $103.98 | A |
| Context window | 1,000,000 | 2,000,000 | B |
| Max output | 65,536 | 8,192 | A |
| Average score | 87.2 | 87.9 | B |
| Arena Elo | 1474.9 | 1478.2 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Max wins 5, GPT-5.1 Max wins 6, and 1 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Max | GPT-5.1 Max | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.1 | 91.3 | 5.2 | GPT-5.1 Max |
| GPQA Diamond | 84.4 | 86.4 | 2.0 | GPT-5.1 Max |
| SWE-bench Verified | 80.2 | 75.6 | 4.6 | Claude Sonnet 4.5 Max |
| HumanEval | 92.4 | 92.2 | 0.2 | Claude Sonnet 4.5 Max |
| MATH-500 | 92.8 | 91.3 | 1.5 | Claude Sonnet 4.5 Max |
| AIME 2025 | 85.4 | 88.8 | 3.4 | GPT-5.1 Max |
| LiveCodeBench | 82.8 | 80.2 | 2.6 | Claude Sonnet 4.5 Max |
| IFEval | 92.9 | 92.2 | 0.7 | Claude Sonnet 4.5 Max |
| TruthfulQA | 87.3 | 91.1 | 3.8 | GPT-5.1 Max |
| HellaSwag | 93.1 | 93.1 | 0.0 | Tie |
| MMMU | 82.0 | 85.1 | 3.1 | GPT-5.1 Max |
| Arena Elo | 1474.9 | 1478.2 | 3.3 | GPT-5.1 Max |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Max costs about $38.79 per million tokens and GPT-5.1 Max costs about $41.37. Claude Sonnet 4.5 Max is roughly 6% 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 1,000,000 for Claude Sonnet 4.5 Max. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Max wins 5, GPT-5.1 Max wins 6, and 1 are tied. On the index average, GPT-5.1 Max leads Claude Sonnet 4.5 Max by 0.7 points (87.9 versus 87.2).
The price picture favours Claude Sonnet 4.5 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 Claude Sonnet 4.5 Max for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Claude Sonnet 4.5 Max if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 65,536-token output limit.
Choose GPT-5.1 Max if
- You want the higher average benchmark score in this index.
- You need the larger 2,000,000-token context window.
FAQ
Is Claude Sonnet 4.5 Max better than GPT-5.1 Max?
On the index average, GPT-5.1 Max leads Claude Sonnet 4.5 Max by 0.7 points (87.9 versus 87.2). The better choice depends on price, context and your task. Claude Sonnet 4.5 Max wins 5 benchmarks, GPT-5.1 Max wins 6.
Which is cheaper, Claude Sonnet 4.5 Max or GPT-5.1 Max?
Claude Sonnet 4.5 Max is cheaper on a blended 3:1 basis at about $38.79 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 Sonnet 4.5 Max has 1,000,000 tokens.
Are these models open weights?
Claude Sonnet 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 Claude Sonnet 4.5 Max for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.