Gemini 3 Flash Pro vs o3 Pro: which model should you choose?
We compared Gemini 3 Flash Pro and o3 Pro on price, context window and 12 benchmarks. o3 Pro has the stronger average benchmark score; o3 Pro is cheaper on a blended 3:1 basis.
Gemini 3 Flash Pro
Gemini 3 Flash Pro is a frontier model from Google DeepMind. It offers a 400,000-token context window, costs $17.71 per million input tokens and $86.50 per million output tokens, and averages 84.8 across the index's benchmark suite.
- Input
- $17.71 / 1M
- Output
- $86.50 / 1M
- Context
- 400,000
- Avg score
- 84.8
- Open weights
- No
o3 Pro
o3 Pro is a frontier model from OpenAI. It offers a 400,000-token context window, costs $17.89 per million input tokens and $81.48 per million output tokens, and averages 85.8 across the index's benchmark suite.
- Input
- $17.89 / 1M
- Output
- $81.48 / 1M
- Context
- 400,000
- Avg score
- 85.8
- Open weights
- No
Specification comparison
| Spec | Gemini 3 Flash Pro | o3 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $17.71 | $17.89 | A |
| Output price / 1M | $86.50 | $81.48 | B |
| Context window | 400,000 | 400,000 | Tie |
| Max output | 4,096 | 8,192 | B |
| Average score | 84.8 | 85.8 | B |
| Arena Elo | 1469.2 | 1471.9 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Gemini 3 Flash Pro wins 2, o3 Pro wins 10, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Gemini 3 Flash Pro | o3 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.0 | 84.3 | 2.7 | Gemini 3 Flash Pro |
| GPQA Diamond | 77.7 | 78.7 | 1.0 | o3 Pro |
| SWE-bench Verified | 73.3 | 76.9 | 3.6 | o3 Pro |
| HumanEval | 89.9 | 90.6 | 0.7 | o3 Pro |
| MATH-500 | 91.8 | 92.4 | 0.6 | o3 Pro |
| AIME 2025 | 79.9 | 83.5 | 3.6 | o3 Pro |
| LiveCodeBench | 80.2 | 82.4 | 2.2 | o3 Pro |
| IFEval | 92.8 | 90.9 | 1.9 | Gemini 3 Flash Pro |
| TruthfulQA | 86.2 | 88.4 | 2.2 | o3 Pro |
| HellaSwag | 90.6 | 92.5 | 1.9 | o3 Pro |
| MMMU | 83.0 | 83.1 | 0.1 | o3 Pro |
| Arena Elo | 1469.2 | 1471.9 | 2.7 | o3 Pro |
Price analysis
On a blended 3:1 input-to-output basis, Gemini 3 Flash Pro costs about $34.91 per million tokens and o3 Pro costs about $33.79. o3 Pro is roughly 3% cheaper than Gemini 3 Flash Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 400,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Gemini 3 Flash Pro wins 2, o3 Pro wins 10, and 0 are tied. On the index average, o3 Pro leads Gemini 3 Flash Pro by 1.0 points (85.8 versus 84.8).
The price picture favours o3 Pro. 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 o3 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Gemini 3 Flash Pro if
- You prefer Google DeepMind's tooling or already use it.
Choose o3 Pro 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 8,192-token output limit.
FAQ
Is Gemini 3 Flash Pro better than o3 Pro?
On the index average, o3 Pro leads Gemini 3 Flash Pro by 1.0 points (85.8 versus 84.8). The better choice depends on price, context and your task. Gemini 3 Flash Pro wins 2 benchmarks, o3 Pro wins 10.
Which is cheaper, Gemini 3 Flash Pro or o3 Pro?
o3 Pro is cheaper on a blended 3:1 basis at about $33.79 per million tokens, versus $34.91 for Gemini 3 Flash Pro.
Which has the larger context window?
Both models list a 400,000-token context window.
Are these models open weights?
Gemini 3 Flash Pro is proprietary; o3 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with o3 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.