Claude Sonnet 4.5 Vision vs o3: which model should you choose?
We compared Claude Sonnet 4.5 Vision and o3 on price, context window and 12 benchmarks. o3 has the stronger average benchmark score; o3 is cheaper on a blended 3:1 basis.
Claude Sonnet 4.5 Vision
Claude Sonnet 4.5 Vision is a frontier model from Anthropic. It offers a 128,000-token context window, costs $16.99 per million input tokens and $82.33 per million output tokens, and averages 83.8 across the index's benchmark suite.
- Input
- $16.99 / 1M
- Output
- $82.33 / 1M
- Context
- 128,000
- Avg score
- 83.8
- 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 Sonnet 4.5 Vision | o3 | Edge |
|---|---|---|---|
| Input price / 1M | $16.99 | $16.80 | B |
| Output price / 1M | $82.33 | $81.80 | B |
| Context window | 128,000 | 400,000 | B |
| Max output | 16,384 | 4,096 | A |
| Average score | 83.8 | 84.5 | B |
| Arena Elo | 1447.6 | 1449.0 | B |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Sonnet 4.5 Vision wins 5, o3 wins 7, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Sonnet 4.5 Vision | o3 | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 84.8 | 86.9 | 2.1 | o3 |
| GPQA Diamond | 79.6 | 78.3 | 1.3 | Claude Sonnet 4.5 Vision |
| SWE-bench Verified | 73.7 | 72.9 | 0.8 | Claude Sonnet 4.5 Vision |
| HumanEval | 87.0 | 89.8 | 2.8 | o3 |
| MATH-500 | 90.6 | 87.9 | 2.7 | Claude Sonnet 4.5 Vision |
| AIME 2025 | 86.4 | 84.4 | 2.0 | Claude Sonnet 4.5 Vision |
| LiveCodeBench | 76.5 | 80.7 | 4.2 | o3 |
| IFEval | 89.9 | 88.7 | 1.2 | Claude Sonnet 4.5 Vision |
| TruthfulQA | 83.7 | 84.6 | 0.9 | o3 |
| HellaSwag | 89.4 | 92.7 | 3.3 | o3 |
| MMMU | 79.7 | 82.3 | 2.6 | o3 |
| Arena Elo | 1447.6 | 1449.0 | 1.4 | o3 |
Price analysis
On a blended 3:1 input-to-output basis, Claude Sonnet 4.5 Vision costs about $33.33 per million tokens and o3 costs about $33.05. o3 is roughly 1% cheaper than Claude Sonnet 4.5 Vision. 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 Sonnet 4.5 Vision. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Sonnet 4.5 Vision wins 5, o3 wins 7, and 0 are tied. On the index average, o3 leads Claude Sonnet 4.5 Vision by 0.7 points (84.5 versus 83.8).
The price picture favours o3. 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 check whether its price holds at your expected volume before committing.
Choose Claude Sonnet 4.5 Vision if
- You need the larger 16,384-token output limit.
Choose o3 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.
FAQ
Is Claude Sonnet 4.5 Vision better than o3?
On the index average, o3 leads Claude Sonnet 4.5 Vision by 0.7 points (84.5 versus 83.8). The better choice depends on price, context and your task. Claude Sonnet 4.5 Vision wins 5 benchmarks, o3 wins 7.
Which is cheaper, Claude Sonnet 4.5 Vision or o3?
o3 is cheaper on a blended 3:1 basis at about $33.05 per million tokens, versus $33.33 for Claude Sonnet 4.5 Vision.
Which has the larger context window?
o3 has the larger context window at 400,000 tokens. Claude Sonnet 4.5 Vision has 128,000 tokens.
Are these models open weights?
Claude Sonnet 4.5 Vision 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 check whether its price holds at your expected volume before committing.