Claude Opus 4.5 vs Claude Sonnet 4.5 Pro: which model should you choose?
We compared Claude Opus 4.5 and Claude Sonnet 4.5 Pro on price, context window and 12 benchmarks. Claude Opus 4.5 has the stronger average benchmark score; Claude Opus 4.5 is cheaper on a blended 3:1 basis.
Claude Opus 4.5
Claude Opus 4.5 is a frontier model from Anthropic. It offers a 400,000-token context window, costs $19.42 per million input tokens and $75.27 per million output tokens, and averages 87.7 across the index's benchmark suite.
- Input
- $19.42 / 1M
- Output
- $75.27 / 1M
- Context
- 400,000
- Avg score
- 87.7
- Open weights
- No
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
Specification comparison
| Spec | Claude Opus 4.5 | Claude Sonnet 4.5 Pro | Edge |
|---|---|---|---|
| Input price / 1M | $19.42 | $18.73 | B |
| Output price / 1M | $75.27 | $82.29 | A |
| Context window | 400,000 | 1,000,000 | B |
| Max output | 4,096 | 16,384 | B |
| Average score | 87.7 | 86.7 | A |
| Arena Elo | 1491.2 | 1469.0 | A |
| Open weights | No | No | Tie |
Benchmark comparison
Claude Opus 4.5 wins 8, Claude Sonnet 4.5 Pro wins 4, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | Claude Opus 4.5 | Claude Sonnet 4.5 Pro | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 87.0 | 86.3 | 0.7 | Claude Opus 4.5 |
| GPQA Diamond | 81.7 | 83.1 | 1.4 | Claude Sonnet 4.5 Pro |
| SWE-bench Verified | 77.1 | 73.9 | 3.2 | Claude Opus 4.5 |
| HumanEval | 93.7 | 92.7 | 1.0 | Claude Opus 4.5 |
| MATH-500 | 93.7 | 90.1 | 3.6 | Claude Opus 4.5 |
| AIME 2025 | 89.8 | 88.4 | 1.4 | Claude Opus 4.5 |
| LiveCodeBench | 85.0 | 81.9 | 3.1 | Claude Opus 4.5 |
| IFEval | 92.5 | 94.1 | 1.6 | Claude Sonnet 4.5 Pro |
| TruthfulQA | 88.1 | 86.1 | 2.0 | Claude Opus 4.5 |
| HellaSwag | 92.4 | 92.6 | 0.2 | Claude Sonnet 4.5 Pro |
| MMMU | 84.2 | 84.5 | 0.3 | Claude Sonnet 4.5 Pro |
| Arena Elo | 1491.2 | 1469.0 | 22.2 | Claude Opus 4.5 |
Price analysis
On a blended 3:1 input-to-output basis, Claude Opus 4.5 costs about $33.38 per million tokens and Claude Sonnet 4.5 Pro costs about $34.62. Claude Opus 4.5 is roughly 4% 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.
Claude Sonnet 4.5 Pro has the larger context window at 1,000,000 tokens, compared with 400,000 for Claude Opus 4.5. That matters for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, Claude Opus 4.5 wins 8, Claude Sonnet 4.5 Pro wins 4, and 0 are tied. On the index average, Claude Opus 4.5 leads Claude Sonnet 4.5 Pro by 1.0 points (87.7 versus 86.7).
The price picture favours Claude Opus 4.5. The context picture favours Claude Sonnet 4.5 Pro. 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 Opus 4.5 for quality-sensitive work, and check whether its price holds at your expected volume before committing.
Choose Claude Opus 4.5 if
- You want the higher average benchmark score in this index.
- Unit cost matters and you want the cheaper blended price.
Choose Claude Sonnet 4.5 Pro if
- You need the larger 1,000,000-token context window.
- You need the larger 16,384-token output limit.
FAQ
Is Claude Opus 4.5 better than Claude Sonnet 4.5 Pro?
On the index average, Claude Opus 4.5 leads Claude Sonnet 4.5 Pro by 1.0 points (87.7 versus 86.7). The better choice depends on price, context and your task. Claude Opus 4.5 wins 8 benchmarks, Claude Sonnet 4.5 Pro wins 4.
Which is cheaper, Claude Opus 4.5 or Claude Sonnet 4.5 Pro?
Claude Opus 4.5 is cheaper on a blended 3:1 basis at about $33.38 per million tokens, versus $34.62 for Claude Sonnet 4.5 Pro.
Which has the larger context window?
Claude Sonnet 4.5 Pro has the larger context window at 1,000,000 tokens. Claude Opus 4.5 has 400,000 tokens.
Are these models open weights?
Claude Opus 4.5 is proprietary; Claude Sonnet 4.5 Pro is proprietary.
Which should I choose for production?
If you need a single default, start with Claude Opus 4.5 for quality-sensitive work, and check whether its price holds at your expected volume before committing.