Claude Sonnet 4.5 Pro vs o4 Pro: which model should you choose?
We compared Claude Sonnet 4.5 Pro and o4 Pro on price, context window and 12 benchmarks. o4 Pro has the stronger average benchmark score; o4 Pro is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Pro
Claude Sonnet 4.5 Pro is a frontier model from Anthropic. It offers a 1,000,000-token context window, costs $18.73 per million input tokens and $82.29 per million output tokens, and averages 86.7 across the index's benchmark suite.
- Input
- $18.73 / 1M
- Output
- $82.29 / 1M
- Context
- 1,000,000
- Avg score
- 86.7
- Open weights
- No
o4 Pro
o4 Pro is a frontier model from OpenAI. It offers a 1,000,000-token context window, costs $19.37 per million input tokens and $70.19 per million output tokens, and averages 87.3 across the index's benchmark suite.
- Input
- $19.37 / 1M
- Output
- $70.19 / 1M
- Context
- 1,000,000
- Avg score
- 87.3
- Open weights
- No
Specification comparison
| Spec | Claude Sonnet 4.5 Pro | o4 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $18.73 | $19.37 | A |
| Output price / 1M | $82.29 | $70.19 | B |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Max output | 16,384 | 16,384 | Tie |
| Average score | 86.7 | 87.3 | B |
| Arena Elo | 1469.0 | 1471.2 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Pro wins 6, o4 Pro wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Pro | o4 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.3 | 87.7 | 1.4 | o4 Pro |
| GPQA Diamond | 83.1 | 82.7 | 0.4 | Claude Sonnet 4.5 Pro |
| SWE-bench Verified | 73.9 | 78.5 | 4.6 | o4 Pro |
| HumanEval | 92.7 | 92.1 | 0.6 | Claude Sonnet 4.5 Pro |
| MATH-500 | 90.1 | 89.8 | 0.3 | Claude Sonnet 4.5 Pro |
| AIME 2025 | 88.4 | 89.9 | 1.5 | o4 Pro |
| LiveCodeBench | 81.9 | 81.8 | 0.1 | Claude Sonnet 4.5 Pro |
| IFEval | 94.1 | 90.9 | 3.2 | Claude Sonnet 4.5 Pro |
| TruthfulQA | 86.1 | 87.9 | 1.8 | o4 Pro |
| HellaSwag | 92.6 | 94.4 | 1.8 | o4 Pro |
| MMMU | 84.5 | 84.1 | 0.4 | Claude Sonnet 4.5 Pro |
| Arena Elo | 1469.0 | 1471.2 | 2.2 | o4 Pro |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Pro costs about $34.62 per million tokens and o4 Pro costs about $32.08. o4 Pro is roughly 7% cheaper than Claude Sonnet 4.5 Pro. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 1,000,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Pro wins 6, o4 Pro wins 6, and 0 are tied. On the index average, o4 Pro leads Claude Sonnet 4.5 Pro by 0.6 points (87.3 versus 86.7).
The price picture favours o4 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 o4 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Sonnet 4.5 Pro if
- You prefer Anthropic's tooling or already use it.
Choose o4 Pro if
- You want the higher average benchmark score in this index.
- Unit cost matters and you want the cheaper blended price.
FAQ
Is Claude Sonnet 4.5 Pro better than o4 Pro?
On the index average, o4 Pro leads Claude Sonnet 4.5 Pro by 0.6 points (87.3 versus 86.7). The better choice depends on price, context and your task. Claude Sonnet 4.5 Pro wins 6 benchmarks, o4 Pro wins 6.
Which is cheaper, Claude Sonnet 4.5 Pro or o4 Pro?
o4 Pro is cheaper on a blended 3:1 basis at about $32.08 per million tokens, versus $34.62 for Claude Sonnet 4.5 Pro.
Which has the larger context window?
Both models list a 1,000,000-token context window.
Are these models open weights?
Claude Sonnet 4.5 Pro is proprietary; o4 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with o4 Pro for quality-sensitive work, and check whether its price holds at your expected volume before committing.