GPT-5.1 Reasoning vs GPT-5.2: which model should you choose?
We compared GPT-5.1 Reasoning and GPT-5.2 on price, context window and 12 benchmarks. GPT-5.1 Reasoning has the stronger average benchmark score; GPT-5.1 Reasoning is cheaper on a blended 3:1 basis.
GPT-5.1 Reasoning
GPT-5.1 Reasoning is a frontier model from OpenAI. It offers a 400,000-token context window, costs $20.27 per million input tokens and $82.11 per million output tokens, and averages 88.3 across the index's benchmark suite.
- Input
- $20.27 / 1M
- Output
- $82.11 / 1M
- Context
- 400,000
- Avg score
- 88.3
- Open weights
- No
GPT-5.2
GPT-5.2 is a frontier model from OpenAI. It offers a 2,000,000-token context window, costs $19.71 per million input tokens and $85.71 per million output tokens, and averages 88.0 across the index's benchmark suite.
- Input
- $19.71 / 1M
- Output
- $85.71 / 1M
- Context
- 2,000,000
- Avg score
- 88.0
- Open weights
- No
Specification comparison
| Spec | GPT-5.1 Reasoning | GPT-5.2 | Edge |
|---|---|---|---|
| Input price / 1M | $20.27 | $19.71 | B |
| Output price / 1M | $82.11 | $85.71 | A |
| Context window | 400,000 | 2,000,000 | B |
| Max output | 128,000 | 16,384 | A |
| Average score | 88.3 | 88.0 | A |
| Arena Elo | 1485.9 | 1478.0 | A |
| Open weights | No | No | Tie |
Benchmark comparison
GPT-5.1 Reasoning wins 10, GPT-5.2 wins 2, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | GPT-5.1 Reasoning | GPT-5.2 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 90.0 | 89.9 | 0.1 | GPT-5.1 Reasoning |
| GPQA Diamond | 85.6 | 84.9 | 0.7 | GPT-5.1 Reasoning |
| SWE-bench Verified | 76.0 | 80.2 | 4.2 | GPT-5.2 |
| HumanEval | 92.9 | 91.0 | 1.9 | GPT-5.1 Reasoning |
| MATH-500 | 95.9 | 90.6 | 5.3 | GPT-5.1 Reasoning |
| AIME 2025 | 85.0 | 90.6 | 5.6 | GPT-5.2 |
| LiveCodeBench | 80.9 | 79.7 | 1.2 | GPT-5.1 Reasoning |
| IFEval | 94.6 | 93.6 | 1.0 | GPT-5.1 Reasoning |
| TruthfulQA | 90.0 | 89.7 | 0.3 | GPT-5.1 Reasoning |
| HellaSwag | 94.4 | 92.6 | 1.8 | GPT-5.1 Reasoning |
| MMMU | 86.2 | 85.3 | 0.9 | GPT-5.1 Reasoning |
| Arena Elo | 1485.9 | 1478.0 | 7.9 | GPT-5.1 Reasoning |
Price analysis
On a blended 3:1 input-to-output basis, GPT-5.1 Reasoning costs about $35.73 per million tokens and GPT-5.2 costs about $36.21. GPT-5.1 Reasoning is roughly 1% cheaper than GPT-5.2. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
GPT-5.2 has the larger context window at 2,000,000 tokens, compared with 400,000 for GPT-5.1 Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, GPT-5.1 Reasoning wins 10, GPT-5.2 wins 2, and 0 are tied. On the index average, GPT-5.1 Reasoning leads GPT-5.2 by 0.3 points (88.3 versus 88.0).
The price picture favours GPT-5.1 Reasoning. The context picture favours GPT-5.2. 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 Reasoning for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose GPT-5.1 Reasoning 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 128,000-token output limit.
Choose GPT-5.2 if
- You need the larger 2,000,000-token context window.
FAQ
Is GPT-5.1 Reasoning better than GPT-5.2?
On the index average, GPT-5.1 Reasoning leads GPT-5.2 by 0.3 points (88.3 versus 88.0). The better choice depends on price, context and your task. GPT-5.1 Reasoning wins 10 benchmarks, GPT-5.2 wins 2.
Which is cheaper, GPT-5.1 Reasoning or GPT-5.2?
GPT-5.1 Reasoning is cheaper on a blended 3:1 basis at about $35.73 per million tokens, versus $36.21 for GPT-5.2.
Which has the larger context window?
GPT-5.2 has the larger context window at 2,000,000 tokens. GPT-5.1 Reasoning has 400,000 tokens.
Are these models open weights?
GPT-5.1 Reasoning is proprietary; GPT-5.2 is proprietary.
Which should I choose for production?
If you need a single default, start with GPT-5.1 Reasoning for quality-sensitive work, and check whether its price holds at your expected volume before committing.