Claude Opus 4.5 vs Gemini 3 Pro Reasoning: which model should you choose?
We compared Claude Opus 4.5 and Gemini 3 Pro Reasoning on price, context window and 12 benchmarks. Claude Opus 4.5 has the stronger average benchmark score; Claude Opus 4.5 is cheaper on a blended 3:1 basis.
Claude Opus 4.5
Claude Opus 4.5 is a frontier model from Anthropic. It offers a 400,000-token context window, costs $19.42 per million input tokens and $75.27 per million output tokens, and averages 87.7 across the index's benchmark suite.
- Input
- $19.42 / 1M
- Output
- $75.27 / 1M
- Context
- 400,000
- Avg score
- 87.7
- Open weights
- No
Gemini 3 Pro Reasoning
Gemini 3 Pro Reasoning is a frontier model from Google DeepMind. It offers a 200,000-token context window, costs $19.69 per million input tokens and $98.36 per million output tokens, and averages 87.5 across the index's benchmark suite.
- Input
- $19.69 / 1M
- Output
- $98.36 / 1M
- Context
- 200,000
- Avg score
- 87.5
- Open weights
- No
Specification comparison
| Spec | Claude Opus 4.5 | Gemini 3 Pro Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $19.42 | $19.69 | A |
| Output price / 1M | $75.27 | $98.36 | A |
| Context window | 400,000 | 200,000 | A |
| Max output | 4,096 | 8,192 | B |
| Average score | 87.7 | 87.5 | A |
| Arena Elo | 1491.2 | 1485.0 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Opus 4.5 wins 7, Gemini 3 Pro Reasoning wins 5, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Opus 4.5 | Gemini 3 Pro Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.0 | 90.1 | 3.1 | Gemini 3 Pro Reasoning |
| GPQA Diamond | 81.7 | 83.9 | 2.2 | Gemini 3 Pro Reasoning |
| SWE-bench Verified | 77.1 | 76.3 | 0.8 | Claude Opus 4.5 |
| HumanEval | 93.7 | 90.2 | 3.5 | Claude Opus 4.5 |
| MATH-500 | 93.7 | 93.3 | 0.4 | Claude Opus 4.5 |
| AIME 2025 | 89.8 | 88.8 | 1.0 | Claude Opus 4.5 |
| LiveCodeBench | 85.0 | 82.0 | 3.0 | Claude Opus 4.5 |
| IFEval | 92.5 | 93.8 | 1.3 | Gemini 3 Pro Reasoning |
| TruthfulQA | 88.1 | 90.3 | 2.2 | Gemini 3 Pro Reasoning |
| HellaSwag | 92.4 | 93.5 | 1.1 | Gemini 3 Pro Reasoning |
| MMMU | 84.2 | 80.8 | 3.4 | Claude Opus 4.5 |
| Arena Elo | 1491.2 | 1485.0 | 6.2 | Claude Opus 4.5 |
Price analysis
On a blended 3:1 input-to-output basis, Claude Opus 4.5 costs about $33.38 per million tokens and Gemini 3 Pro Reasoning costs about $39.36. Claude Opus 4.5 is roughly 15% cheaper than Gemini 3 Pro Reasoning. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Claude Opus 4.5 has the larger context window at 400,000 tokens, compared with 200,000 for Gemini 3 Pro Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Opus 4.5 wins 7, Gemini 3 Pro Reasoning wins 5, and 0 are tied. On the index average, Claude Opus 4.5 leads Gemini 3 Pro Reasoning by 0.2 points (87.7 versus 87.5).
The price picture favours Claude Opus 4.5. The context picture favours Claude Opus 4.5. 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 Claude Opus 4.5 for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Opus 4.5 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.
Choose Gemini 3 Pro Reasoning if
- You need the larger 8,192-token output limit.
FAQ
Is Claude Opus 4.5 better than Gemini 3 Pro Reasoning?
On the index average, Claude Opus 4.5 leads Gemini 3 Pro Reasoning by 0.2 points (87.7 versus 87.5). The better choice depends on price, context and your task. Claude Opus 4.5 wins 7 benchmarks, Gemini 3 Pro Reasoning wins 5.
Which is cheaper, Claude Opus 4.5 or Gemini 3 Pro Reasoning?
Claude Opus 4.5 is cheaper on a blended 3:1 basis at about $33.38 per million tokens, versus $39.36 for Gemini 3 Pro Reasoning.
Which has the larger context window?
Claude Opus 4.5 has the larger context window at 400,000 tokens. Gemini 3 Pro Reasoning has 200,000 tokens.
Are these models open weights?
Claude Opus 4.5 is proprietary; Gemini 3 Pro Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Opus 4.5 for quality-sensitive work, and check whether its price holds at your expected volume before committing.