Gemini 3 Pro vs GPT-5.1: which model should you choose?
We compared Gemini 3 Pro and GPT-5.1 on price, context window and 12 benchmarks. Gemini 3 Pro has the stronger average benchmark score; GPT-5.1 is cheaper on a blended 3:1 basis.
Gemini 3 Pro
Gemini 3 Pro is a frontier model from Google DeepMind. It offers a 2,000,000-token context window, costs $18.24 per million input tokens and $82.93 per million output tokens, and averages 86.1 across the index's benchmark suite.
- Input
- $18.24 / 1M
- Output
- $82.93 / 1M
- Context
- 2,000,000
- Avg score
- 86.1
- Open weights
- No
GPT-5.1
GPT-5.1 is a frontier model from OpenAI. It offers a 2,000,000-token context window, costs $19.01 per million input tokens and $69.84 per million output tokens, and averages 86.0 across the index's benchmark suite.
- Input
- $19.01 / 1M
- Output
- $69.84 / 1M
- Context
- 2,000,000
- Avg score
- 86.0
- Open weights
- No
Specification comparison
| Spec | Gemini 3 Pro | GPT-5.1 | Edge |
|---|---|---|---|
| Input price / 1M | $18.24 | $19.01 | A |
| Output price / 1M | $82.93 | $69.84 | B |
| Context window | 2,000,000 | 2,000,000 | Tie |
| Max output | 8,192 | 128,000 | B |
| Average score | 86.1 | 86.0 | A |
| Arena Elo | 1460.7 | 1462.5 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 3 Pro wins 5, GPT-5.1 wins 7, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 3 Pro | GPT-5.1 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 88.2 | 86.1 | 2.1 | Gemini 3 Pro |
| GPQA Diamond | 79.0 | 82.3 | 3.3 | GPT-5.1 |
| SWE-bench Verified | 78.5 | 76.1 | 2.4 | Gemini 3 Pro |
| HumanEval | 91.8 | 90.6 | 1.2 | Gemini 3 Pro |
| MATH-500 | 89.9 | 90.5 | 0.6 | GPT-5.1 |
| AIME 2025 | 84.3 | 85.6 | 1.3 | GPT-5.1 |
| LiveCodeBench | 83.3 | 78.9 | 4.4 | Gemini 3 Pro |
| IFEval | 93.7 | 90.9 | 2.8 | Gemini 3 Pro |
| TruthfulQA | 88.8 | 89.2 | 0.4 | GPT-5.1 |
| HellaSwag | 91.3 | 92.2 | 0.9 | GPT-5.1 |
| MMMU | 78.6 | 83.3 | 4.7 | GPT-5.1 |
| Arena Elo | 1460.7 | 1462.5 | 1.8 | GPT-5.1 |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 3 Pro costs about $34.41 per million tokens and GPT-5.1 costs about $31.72. GPT-5.1 is roughly 8% cheaper than Gemini 3 Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 2,000,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 3 Pro wins 5, GPT-5.1 wins 7, and 0 are tied. On the index average, Gemini 3 Pro leads GPT-5.1 by 0.1 points (86.1 versus 86.0).
The price picture favours GPT-5.1. 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 Gemini 3 Pro for quality-sensitive work and GPT-5.1 for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Gemini 3 Pro if
- You want the higher average benchmark score in this index.
Choose GPT-5.1 if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 128,000-token output limit.
FAQ
Is Gemini 3 Pro better than GPT-5.1?
On the index average, Gemini 3 Pro leads GPT-5.1 by 0.1 points (86.1 versus 86.0). The better choice depends on price, context and your task. Gemini 3 Pro wins 5 benchmarks, GPT-5.1 wins 7.
Which is cheaper, Gemini 3 Pro or GPT-5.1?
GPT-5.1 is cheaper on a blended 3:1 basis at about $31.72 per million tokens, versus $34.41 for Gemini 3 Pro.
Which has the larger context window?
Both models list a 2,000,000-token context window.
Are these models open weights?
Gemini 3 Pro is proprietary; GPT-5.1 is proprietary.
Which should I choose for production?
If you need a single default, start with Gemini 3 Pro for quality-sensitive work and GPT-5.1 for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.