Claude 3.7 Sonnet Reasoning vs o3: which model should you choose?
We compared Claude 3.7 Sonnet Reasoning and o3 on price, context window and 12 benchmarks. o3 has the stronger average benchmark score; Claude 3.7 Sonnet Reasoning is cheaper on a blended 3:1 basis.
Claude 3.7 Sonnet Reasoning
Claude 3.7 Sonnet Reasoning is a frontier model from Anthropic. It offers a 128,000-token context window, costs $16.30 per million input tokens and $77.62 per million output tokens, and averages 83.7 across the index's benchmark suite.
- Input
- $16.30 / 1M
- Output
- $77.62 / 1M
- Context
- 128,000
- Avg score
- 83.7
- Open weights
- No
o3
o3 is a frontier model from OpenAI. It offers a 400,000-token context window, costs $16.80 per million input tokens and $81.80 per million output tokens, and averages 84.5 across the index's benchmark suite.
- Input
- $16.80 / 1M
- Output
- $81.80 / 1M
- Context
- 400,000
- Avg score
- 84.5
- Open weights
- No
Specification comparison
| Spec | Claude 3.7 Sonnet Reasoning | o3 | Edge |
|---|---|---|---|
| Input price / 1M | $16.30 | $16.80 | A |
| Output price / 1M | $77.62 | $81.80 | A |
| Context window | 128,000 | 400,000 | B |
| Max output | 128,000 | 4,096 | A |
| Average score | 83.7 | 84.5 | B |
| Arena Elo | 1464.4 | 1449.0 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude 3.7 Sonnet Reasoning wins 5, o3 wins 7, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude 3.7 Sonnet Reasoning | o3 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.4 | 86.9 | 0.5 | o3 |
| GPQA Diamond | 81.3 | 78.3 | 3.0 | Claude 3.7 Sonnet Reasoning |
| SWE-bench Verified | 71.0 | 72.9 | 1.9 | o3 |
| HumanEval | 89.2 | 89.8 | 0.6 | o3 |
| MATH-500 | 90.3 | 87.9 | 2.4 | Claude 3.7 Sonnet Reasoning |
| AIME 2025 | 79.8 | 84.4 | 4.6 | o3 |
| LiveCodeBench | 79.6 | 80.7 | 1.1 | o3 |
| IFEval | 90.1 | 88.7 | 1.4 | Claude 3.7 Sonnet Reasoning |
| TruthfulQA | 86.2 | 84.6 | 1.6 | Claude 3.7 Sonnet Reasoning |
| HellaSwag | 90.4 | 92.7 | 2.3 | o3 |
| MMMU | 76.5 | 82.3 | 5.8 | o3 |
| Arena Elo | 1464.4 | 1449.0 | 15.4 | Claude 3.7 Sonnet Reasoning |
Price analysis
On a blended 3:1 input-to-output basis, Claude 3.7 Sonnet Reasoning costs about $31.63 per million tokens and o3 costs about $33.05. Claude 3.7 Sonnet Reasoning is roughly 4% cheaper than o3. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
o3 has the larger context window at 400,000 tokens, compared with 128,000 for Claude 3.7 Sonnet Reasoning. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude 3.7 Sonnet Reasoning wins 5, o3 wins 7, and 0 are tied. On the index average, o3 leads Claude 3.7 Sonnet Reasoning by 0.8 points (84.5 versus 83.7).
The price picture favours Claude 3.7 Sonnet Reasoning. The context picture favours o3. 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 for quality-sensitive work and Claude 3.7 Sonnet Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose Claude 3.7 Sonnet Reasoning if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 128,000-token output limit.
Choose o3 if
- You want the higher average benchmark score in this index.
- You need the larger 400,000-token context window.
FAQ
Is Claude 3.7 Sonnet Reasoning better than o3?
On the index average, o3 leads Claude 3.7 Sonnet Reasoning by 0.8 points (84.5 versus 83.7). The better choice depends on price, context and your task. Claude 3.7 Sonnet Reasoning wins 5 benchmarks, o3 wins 7.
Which is cheaper, Claude 3.7 Sonnet Reasoning or o3?
Claude 3.7 Sonnet Reasoning is cheaper on a blended 3:1 basis at about $31.63 per million tokens, versus $33.05 for o3.
Which has the larger context window?
o3 has the larger context window at 400,000 tokens. Claude 3.7 Sonnet Reasoning has 128,000 tokens.
Are these models open weights?
Claude 3.7 Sonnet Reasoning is proprietary; o3 is proprietary.
Which should I choose for production?
If you need a single default, start with o3 for quality-sensitive work and Claude 3.7 Sonnet Reasoning for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.