Claude Sonnet 4.5 Reasoning vs Gemini 3 Pro Reasoning: which model should you choose?
We compared Claude Sonnet 4.5 Reasoning and Gemini 3 Pro Reasoning on price, context window and 12 benchmarks. Claude Sonnet 4.5 Reasoning has the stronger average benchmark score; Claude Sonnet 4.5 Reasoning is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Reasoning
Claude Sonnet 4.5 Reasoning is a frontier model from Anthropic. It offers a 400,000-token context window, costs $19.48 per million input tokens and $68.20 per million output tokens, and averages 87.7 across the index's benchmark suite.
- Input
- $19.48 / 1M
- Output
- $68.20 / 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 Sonnet 4.5 Reasoning | Gemini 3 Pro Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $19.48 | $19.69 | A |
| Output price / 1M | $68.20 | $98.36 | A |
| Context window | 400,000 | 200,000 | A |
| Max output | 8,192 | 8,192 | Tie |
| Average score | 87.7 | 87.5 | A |
| Arena Elo | 1486.5 | 1485.0 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Reasoning 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 Sonnet 4.5 Reasoning | Gemini 3 Pro Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.6 | 90.1 | 2.5 | Gemini 3 Pro Reasoning |
| GPQA Diamond | 85.2 | 83.9 | 1.3 | Claude Sonnet 4.5 Reasoning |
| SWE-bench Verified | 79.6 | 76.3 | 3.3 | Claude Sonnet 4.5 Reasoning |
| HumanEval | 90.3 | 90.2 | 0.1 | Claude Sonnet 4.5 Reasoning |
| MATH-500 | 89.7 | 93.3 | 3.6 | Gemini 3 Pro Reasoning |
| AIME 2025 | 87.3 | 88.8 | 1.5 | Gemini 3 Pro Reasoning |
| LiveCodeBench | 85.1 | 82.0 | 3.1 | Claude Sonnet 4.5 Reasoning |
| IFEval | 91.9 | 93.8 | 1.9 | Gemini 3 Pro Reasoning |
| TruthfulQA | 87.6 | 90.3 | 2.7 | Gemini 3 Pro Reasoning |
| HellaSwag | 95.2 | 93.5 | 1.7 | Claude Sonnet 4.5 Reasoning |
| MMMU | 85.2 | 80.8 | 4.4 | Claude Sonnet 4.5 Reasoning |
| Arena Elo | 1486.5 | 1485.0 | 1.5 | Claude Sonnet 4.5 Reasoning |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Reasoning costs about $31.66 per million tokens and Gemini 3 Pro Reasoning costs about $39.36. Claude Sonnet 4.5 Reasoning is roughly 20% 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 Sonnet 4.5 Reasoning 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 Sonnet 4.5 Reasoning wins 7, Gemini 3 Pro Reasoning wins 5, and 0 are tied. On the index average, Claude Sonnet 4.5 Reasoning leads Gemini 3 Pro Reasoning by 0.2 points (87.7 versus 87.5).
The price picture favours Claude Sonnet 4.5 Reasoning. The context picture favours Claude Sonnet 4.5 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 Claude Sonnet 4.5 Reasoning for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Sonnet 4.5 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.
Choose Gemini 3 Pro Reasoning if
- You prefer Google DeepMind's tooling or already use it.
FAQ
Is Claude Sonnet 4.5 Reasoning better than Gemini 3 Pro Reasoning?
On the index average, Claude Sonnet 4.5 Reasoning 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 Sonnet 4.5 Reasoning wins 7 benchmarks, Gemini 3 Pro Reasoning wins 5.
Which is cheaper, Claude Sonnet 4.5 Reasoning or Gemini 3 Pro Reasoning?
Claude Sonnet 4.5 Reasoning is cheaper on a blended 3:1 basis at about $31.66 per million tokens, versus $39.36 for Gemini 3 Pro Reasoning.
Which has the larger context window?
Claude Sonnet 4.5 Reasoning has the larger context window at 400,000 tokens. Gemini 3 Pro Reasoning has 200,000 tokens.
Are these models open weights?
Claude Sonnet 4.5 Reasoning is proprietary; Gemini 3 Pro Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Sonnet 4.5 Reasoning for quality-sensitive work, and check whether its price holds at your expected volume before committing.