Claude Opus 5.5 vs Claude Sonnet 5.5: Specs & Benchmark Comparison
Claude Opus 5.5 and Claude Sonnet 5.5 both come from Anthropic, and both were released in September 2026.
The two models share 29 published benchmarks. Claude Opus 5.5 leads on 18 of them, Claude Sonnet 5.5 on 10. The widest gaps are on Program Bench, where Claude Opus 5.5 scores 91.2% against 79.7%; SWE-Bench Pro, where Claude Opus 5.5 scores 89.9% against 81.3%. Averaged across everything we track, Claude Opus 5.5 sits at 71.1% and Claude Sonnet 5.5 at 67.4%.
Claude Sonnet 5.5 is the cheaper API at $2 per million input tokens and $10 per million output tokens, roughly 2 times cheaper than Claude Opus 5.5 at $4 and $20. Both accept a context window of about 1M tokens. Both accept text and images as input.
| Characteristic | Claude Opus 5.5 | Claude Sonnet 5.5 |
|---|---|---|
| Company | Anthropic | Anthropic |
| Release Date | September 22, 2026 | September 28, 2026 |
| Parameters | — | — |
| Multimodal | Yes | Yes |
| Context (input) | 1.0M | 1.0M |
| Context (output) | 128K | 128K |
| Input Price / 1M | $4.00 | $2.00 |
| Output Price / 1M | $20.00 | $10.00 |
| Average Score | 71.1% | 67.4% |
| Benchmarks | ||
| Program Bench | 91.2% | 79.7% |
| SWE-Bench Pro | 89.9% | 81.3% |
| Humanity's Last Exam (no tools, text-only) | 64.4% | 56.9% |
| SWE-Bench Multimodal | 61.4% | 54.3% |
| HealthBench | 60.6% | 65.4% |
| AutomationBench | 40.0% | 44.7% |
| ArXivMath | 91.2% | 86.8% |
| Terminal-Bench 4.0 | 66.4% | 70.6% |
| HealthBench Professional | 65.6% | 69.2% |
| SWE-bench Multilingual | 93.9% | 90.3% |
| Legal Agent Benchmark | 8.3% | 11.7% |
| DeepSWE 1.1 | 74.2% | 71.0% |
| FrontierCode 1.1 | 54.4% | 52.1% |
| CursorBench 4.0 | 57.8% | 55.5% |
| Global-MMLU | 94.3% | 92.1% |
| LatchBio SingleCellBench | 61.2% | 59.1% |
| OfficeQA Pro | 67.7% | 65.6% |
| OfficeQA | 78.9% | 76.9% |
| BenchCAD | 73.0% | 74.7% |
| MILU | 93.1% | 91.6% |
| Chartography | 89.0% | 90.2% |
| Terminal-Bench-Science 0.1 | 58.7% | 59.9% |
| LatchBio SpatialBench Verified | 72.0% | 72.5% |
| FrontierSWE V2 | 62.3% | 61.9% |
| AA-Briefcase v1.1 | 60.7% | 60.4% |
| BenchCAD (with Python tool) | 96.2% | 96.3% |
| BioMysteryBench | 89.3% | 89.2% |
| GDPval-AA 2.1 | 61.5% | 61.5% |
| Toolathlon-Verified | 77.8% | 77.8% |
Visual Benchmark Comparison
Verdict
Claude Sonnet 5.5 leads in 1 out of 4 comparison categories.
Both models show comparable average scores: Claude Opus 5.5 — 0.7, Claude Sonnet 5.5 — 0.7.
Claude Sonnet 5.5 is 2.0x cheaper: input $2.00/1M vs $4.00/1M tokens.
Same context size: 1M tokens.
Both models were released around the same time: 9/22/2026 and 9/28/2026.
More About These Models
Related Comparisons
Frequently Asked Questions
Which is better for coding — Claude Opus 5.5 or Claude Sonnet 5.5?
Which model is cheaper — Claude Opus 5.5 or Claude Sonnet 5.5?
Which has a larger context window — Claude Opus 5.5 or Claude Sonnet 5.5?
The Claude Opus 5.5 and Claude Sonnet 5.5 comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the Claude Opus 5.5 or Claude Sonnet 5.5 page. See also the complete list of AI model comparisons.