Gemini 3 Pro Pro vs GPT-5.1 Reasoning: which model should you choose?
We compared Gemini 3 Pro Pro and GPT-5.1 Reasoning 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.
Gemini 3 Pro Pro
Gemini 3 Pro Pro is a frontier model from Google DeepMind. It offers a 200,000-token context window, costs $19.80 per million input tokens and $108.61 per million output tokens, and averages 87.3 across the index's benchmark suite.
- Input
- $19.80 / 1M
- Output
- $108.61 / 1M
- Context
- 200,000
- Avg score
- 87.3
- Open weights
- No
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
Specification comparison
| Spec | Gemini 3 Pro Pro | GPT-5.1 Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $19.80 | $20.27 | A |
| Output price / 1M | $108.61 | $82.11 | B |
| Context window | 200,000 | 400,000 | B |
| Max output | 8,192 | 128,000 | B |
| Average score | 87.3 | 88.3 | B |
| Arena Elo | 1484.4 | 1485.9 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 3 Pro Pro wins 3, GPT-5.1 Reasoning wins 9, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 3 Pro Pro | GPT-5.1 Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 88.2 | 90.0 | 1.8 | GPT-5.1 Reasoning |
| GPQA Diamond | 81.4 | 85.6 | 4.2 | GPT-5.1 Reasoning |
| SWE-bench Verified | 75.7 | 76.0 | 0.3 | GPT-5.1 Reasoning |
| HumanEval | 95.0 | 92.9 | 2.1 | Gemini 3 Pro Pro |
| MATH-500 | 91.6 | 95.9 | 4.3 | GPT-5.1 Reasoning |
| AIME 2025 | 88.0 | 85.0 | 3.0 | Gemini 3 Pro Pro |
| LiveCodeBench | 83.1 | 80.9 | 2.2 | Gemini 3 Pro Pro |
| IFEval | 92.7 | 94.6 | 1.9 | GPT-5.1 Reasoning |
| TruthfulQA | 87.6 | 90.0 | 2.4 | GPT-5.1 Reasoning |
| HellaSwag | 93.6 | 94.4 | 0.8 | GPT-5.1 Reasoning |
| MMMU | 83.2 | 86.2 | 3.0 | GPT-5.1 Reasoning |
| Arena Elo | 1484.4 | 1485.9 | 1.5 | GPT-5.1 Reasoning |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 3 Pro Pro costs about $42.00 per million tokens and GPT-5.1 Reasoning costs about $35.73. GPT-5.1 Reasoning is roughly 15% cheaper than Gemini 3 Pro Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
GPT-5.1 Reasoning has the larger context window at 400,000 tokens, compared with 200,000 for Gemini 3 Pro Pro. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 3 Pro Pro wins 3, GPT-5.1 Reasoning wins 9, and 0 are tied. On the index average, GPT-5.1 Reasoning leads Gemini 3 Pro Pro by 1.0 points (88.3 versus 87.3).
The price picture favours GPT-5.1 Reasoning. The context picture favours GPT-5.1 Reasoning. 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 Gemini 3 Pro Pro if
- You prefer Google DeepMind's tooling or already use it.
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 400,000-token context window.
- You need the larger 128,000-token output limit.
FAQ
Is Gemini 3 Pro Pro better than GPT-5.1 Reasoning?
On the index average, GPT-5.1 Reasoning leads Gemini 3 Pro Pro by 1.0 points (88.3 versus 87.3). The better choice depends on price, context and your task. Gemini 3 Pro Pro wins 3 benchmarks, GPT-5.1 Reasoning wins 9.
Which is cheaper, Gemini 3 Pro Pro or GPT-5.1 Reasoning?
GPT-5.1 Reasoning is cheaper on a blended 3:1 basis at about $35.73 per million tokens, versus $42.00 for Gemini 3 Pro Pro.
Which has the larger context window?
GPT-5.1 Reasoning has the larger context window at 400,000 tokens. Gemini 3 Pro Pro has 200,000 tokens.
Are these models open weights?
Gemini 3 Pro Pro is proprietary; GPT-5.1 Reasoning 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.