Claude Sonnet 4.5 Max vs GPT-5.2 Reasoning: which model should you choose?
We compared Claude Sonnet 4.5 Max and GPT-5.2 Reasoning on price, context window and 12 benchmarks. GPT-5.2 Reasoning 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-5.2 Reasoning
GPT-5.2 Reasoning is a frontier model from OpenAI. It offers a 1,000,000-token context window, costs $20.98 per million input tokens and $102.78 per million output tokens, and averages 87.5 across the index's benchmark suite.
- Input
- $20.98 / 1M
- Output
- $102.78 / 1M
- Context
- 1,000,000
- Avg score
- 87.5
- Open weights
- No
Specification comparison
| Spec | Claude Sonnet 4.5 Max | GPT-5.2 Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $19.90 | $20.98 | A |
| Output price / 1M | $95.47 | $102.78 | A |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Max output | 65,536 | 65,536 | Tie |
| Average score | 87.2 | 87.5 | B |
| Arena Elo | 1474.9 | 1500.4 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Max wins 5, GPT-5.2 Reasoning 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-5.2 Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.1 | 87.0 | 0.9 | GPT-5.2 Reasoning |
| GPQA Diamond | 84.4 | 87.0 | 2.6 | GPT-5.2 Reasoning |
| SWE-bench Verified | 80.2 | 78.2 | 2.0 | Claude Sonnet 4.5 Max |
| HumanEval | 92.4 | 92.4 | 0.0 | Tie |
| MATH-500 | 92.8 | 91.4 | 1.4 | Claude Sonnet 4.5 Max |
| AIME 2025 | 85.4 | 84.9 | 0.5 | Claude Sonnet 4.5 Max |
| LiveCodeBench | 82.8 | 84.6 | 1.8 | GPT-5.2 Reasoning |
| IFEval | 92.9 | 95.0 | 2.1 | GPT-5.2 Reasoning |
| TruthfulQA | 87.3 | 88.2 | 0.9 | GPT-5.2 Reasoning |
| HellaSwag | 93.1 | 92.5 | 0.6 | Claude Sonnet 4.5 Max |
| MMMU | 82.0 | 81.5 | 0.5 | Claude Sonnet 4.5 Max |
| Arena Elo | 1474.9 | 1500.4 | 25.5 | GPT-5.2 Reasoning |
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-5.2 Reasoning costs about $41.43. Claude Sonnet 4.5 Max is roughly 6% cheaper than GPT-5.2 Reasoning. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 1,000,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Max wins 5, GPT-5.2 Reasoning wins 6, and 1 are tied. On the index average, GPT-5.2 Reasoning leads Claude Sonnet 4.5 Max by 0.3 points (87.5 versus 87.2).
The price picture favours Claude Sonnet 4.5 Max. The context picture is effectively a tie. 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-5.2 Reasoning 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.
Choose GPT-5.2 Reasoning if
- You want the higher average benchmark score in this index.
FAQ
Is Claude Sonnet 4.5 Max better than GPT-5.2 Reasoning?
On the index average, GPT-5.2 Reasoning leads Claude Sonnet 4.5 Max by 0.3 points (87.5 versus 87.2). The better choice depends on price, context and your task. Claude Sonnet 4.5 Max wins 5 benchmarks, GPT-5.2 Reasoning wins 6.
Which is cheaper, Claude Sonnet 4.5 Max or GPT-5.2 Reasoning?
Claude Sonnet 4.5 Max is cheaper on a blended 3:1 basis at about $38.79 per million tokens, versus $41.43 for GPT-5.2 Reasoning.
Which has the larger context window?
Both models list a 1,000,000-token context window.
Are these models open weights?
Claude Sonnet 4.5 Max is proprietary; GPT-5.2 Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with GPT-5.2 Reasoning 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.