Claude Sonnet 4.5 Max vs o4 Reasoning: which model should you choose?
We compared Claude Sonnet 4.5 Max and o4 Reasoning on price, context window and 12 benchmarks. o4 Reasoning has the stronger average benchmark score; Claude Sonnet 4.5 Max is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Max
Claude Sonnet 4.5 Max is a frontier model from Anthropic. It offers a 1,000,000-token context window, costs $19.90 per million input tokens and $95.47 per million output tokens, and averages 87.2 across the index's benchmark suite.
- Input
- $19.90 / 1M
- Output
- $95.47 / 1M
- Context
- 1,000,000
- Avg score
- 87.2
- Open weights
- No
o4 Reasoning
o4 Reasoning is a frontier model from OpenAI. It offers a 1,000,000-token context window, costs $19.69 per million input tokens and $103.53 per million output tokens, and averages 87.5 across the index's benchmark suite.
- Input
- $19.69 / 1M
- Output
- $103.53 / 1M
- Context
- 1,000,000
- Avg score
- 87.5
- Open weights
- No
Specification comparison
| Spec | Claude Sonnet 4.5 Max | o4 Reasoning | Edge |
|---|---|---|---|
| Input price / 1M | $19.90 | $19.69 | B |
| Output price / 1M | $95.47 | $103.53 | A |
| Context window | 1,000,000 | 1,000,000 | Tie |
| Max output | 65,536 | 128,000 | B |
| Average score | 87.2 | 87.5 | B |
| Arena Elo | 1474.9 | 1472.2 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Max wins 6, o4 Reasoning wins 5, and 1 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Max | o4 Reasoning | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 86.1 | 86.1 | 0.0 | Tie |
| GPQA Diamond | 84.4 | 84.0 | 0.4 | Claude Sonnet 4.5 Max |
| SWE-bench Verified | 80.2 | 76.4 | 3.8 | Claude Sonnet 4.5 Max |
| HumanEval | 92.4 | 90.2 | 2.2 | Claude Sonnet 4.5 Max |
| MATH-500 | 92.8 | 94.8 | 2.0 | o4 Reasoning |
| AIME 2025 | 85.4 | 90.3 | 4.9 | o4 Reasoning |
| LiveCodeBench | 82.8 | 83.4 | 0.6 | o4 Reasoning |
| IFEval | 92.9 | 94.5 | 1.6 | o4 Reasoning |
| TruthfulQA | 87.3 | 89.0 | 1.7 | o4 Reasoning |
| HellaSwag | 93.1 | 92.4 | 0.7 | Claude Sonnet 4.5 Max |
| MMMU | 82.0 | 81.8 | 0.2 | Claude Sonnet 4.5 Max |
| Arena Elo | 1474.9 | 1472.2 | 2.7 | Claude Sonnet 4.5 Max |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Max costs about $38.79 per million tokens and o4 Reasoning costs about $40.65. Claude Sonnet 4.5 Max is roughly 5% cheaper than o4 Reasoning. 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 Max wins 6, o4 Reasoning wins 5, and 1 are tied. On the index average, o4 Reasoning leads Claude Sonnet 4.5 Max by 0.3 points (87.5 versus 87.2).
The price picture favours Claude Sonnet 4.5 Max. 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 Reasoning for quality-sensitive work and Claude Sonnet 4.5 Max 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 Max if
- Unit cost matters and you want the cheaper blended price.
Choose o4 Reasoning if
- You want the higher average benchmark score in this index.
- You need the larger 128,000-token output limit.
FAQ
Is Claude Sonnet 4.5 Max better than o4 Reasoning?
On the index average, o4 Reasoning leads Claude Sonnet 4.5 Max by 0.3 points (87.5 versus 87.2). The better choice depends on price, context and your task. Claude Sonnet 4.5 Max wins 6 benchmarks, o4 Reasoning wins 5.
Which is cheaper, Claude Sonnet 4.5 Max or o4 Reasoning?
Claude Sonnet 4.5 Max is cheaper on a blended 3:1 basis at about $38.79 per million tokens, versus $40.65 for o4 Reasoning.
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 Max is proprietary; o4 Reasoning is proprietary.
Which should I choose for production?
If you need a single default, start with o4 Reasoning for quality-sensitive work and Claude Sonnet 4.5 Max for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.