Claude Sonnet 4.5 Turbo vs o3 Pro: which model should you choose?
We compared Claude Sonnet 4.5 Turbo and o3 Pro on price, context window and 12 benchmarks. Claude Sonnet 4.5 Turbo has the stronger average benchmark score; o3 Pro is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Turbo
Claude Sonnet 4.5 Turbo is a frontier model from Anthropic. It offers a 1,000,000-token context window, costs $18.37 per million input tokens and $81.65 per million output tokens, and averages 85.9 across the index's benchmark suite.
- Input
- $18.37 / 1M
- Output
- $81.65 / 1M
- Context
- 1,000,000
- Avg score
- 85.9
- 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 | Claude Sonnet 4.5 Turbo | o3 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $18.37 | $17.89 | B |
| Output price / 1M | $81.65 | $81.48 | B |
| Context window | 1,000,000 | 400,000 | A |
| Max output | 65,536 | 8,192 | A |
| Average score | 85.9 | 85.8 | A |
| Arena Elo | 1461.7 | 1471.9 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Turbo wins 5, o3 Pro wins 7, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Turbo | o3 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.2 | 84.3 | 2.9 | Claude Sonnet 4.5 Turbo |
| GPQA Diamond | 83.7 | 78.7 | 5.0 | Claude Sonnet 4.5 Turbo |
| SWE-bench Verified | 75.2 | 76.9 | 1.7 | o3 Pro |
| HumanEval | 90.4 | 90.6 | 0.2 | o3 Pro |
| MATH-500 | 88.0 | 92.4 | 4.4 | o3 Pro |
| AIME 2025 | 87.8 | 83.5 | 4.3 | Claude Sonnet 4.5 Turbo |
| LiveCodeBench | 78.9 | 82.4 | 3.5 | o3 Pro |
| IFEval | 91.4 | 90.9 | 0.5 | Claude Sonnet 4.5 Turbo |
| TruthfulQA | 87.7 | 88.4 | 0.7 | o3 Pro |
| HellaSwag | 93.9 | 92.5 | 1.4 | Claude Sonnet 4.5 Turbo |
| MMMU | 81.1 | 83.1 | 2.0 | o3 Pro |
| Arena Elo | 1461.7 | 1471.9 | 10.2 | o3 Pro |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Turbo costs about $34.19 per million tokens and o3 Pro costs about $33.79. o3 Pro is roughly 1% cheaper than Claude Sonnet 4.5 Turbo. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Claude Sonnet 4.5 Turbo has the larger context window at 1,000,000 tokens, compared with 400,000 for o3 Pro. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Turbo wins 5, o3 Pro wins 7, and 0 are tied. On the index average, Claude Sonnet 4.5 Turbo leads o3 Pro by 0.1 points (85.9 versus 85.8).
The price picture favours o3 Pro. The context picture favours Claude Sonnet 4.5 Turbo. 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 Turbo for quality-sensitive work and o3 Pro for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Claude Sonnet 4.5 Turbo if
- You want the higher average benchmark score in this index.
- You need the larger 1,000,000-token context window.
- You need the larger 65,536-token output limit.
Choose o3 Pro if
- Unit cost matters and you want the cheaper blended price.
FAQ
Is Claude Sonnet 4.5 Turbo better than o3 Pro?
On the index average, Claude Sonnet 4.5 Turbo leads o3 Pro by 0.1 points (85.9 versus 85.8). The better choice depends on price, context and your task. Claude Sonnet 4.5 Turbo wins 5 benchmarks, o3 Pro wins 7.
Which is cheaper, Claude Sonnet 4.5 Turbo or o3 Pro?
o3 Pro is cheaper on a blended 3:1 basis at about $33.79 per million tokens, versus $34.19 for Claude Sonnet 4.5 Turbo.
Which has the larger context window?
Claude Sonnet 4.5 Turbo has the larger context window at 1,000,000 tokens. o3 Pro has 400,000 tokens.
Are these models open weights?
Claude Sonnet 4.5 Turbo is proprietary; o3 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Sonnet 4.5 Turbo for quality-sensitive work and o3 Pro for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.