Claude Sonnet 4.5 vs GPT-5.5
Claude Sonnet 4.5 
GPT-5.5 Verdict
- GPT-5.5 leads on quality: 65.0 vs 57.9.
- GPT-5.5 is stronger in coding, human preference, reasoning, agents & tools, composite, instruction following, knowledge, long context, multimodal.
- Claude Sonnet 4.5 (high) is 1.9× cheaper ($6.00 vs $11.25 per 1M blended).
- GPT-5.5 streams 2.3× faster (91 vs 40 tokens per second).
| Metric | Claude Sonnet 4.5 (high) | GPT-5.5 |
|---|---|---|
| BenchLeader Index | 57.9 | 65.0 |
| Coding score | 56.4 | 57.2 |
| Human preference score | 65.3 | 67.7 |
| Reasoning score | 66.4 | 70.0 |
| Agents & tools score | – | 67.6 |
| Composite score | – | 71.1 |
| Instruction following score | – | 70.5 |
| Knowledge score | – | 70.5 |
| Long context score | – | 66.6 |
| Multimodal score | – | 64.3 |
| Blended price $/M | $6.00 | $11.25 |
| Output speed | 40 tok/s | 91 tok/s |
| Time to first answer | 1.2 s | 49.6 s |
| Context window | 1M | 1.1M |
| Terminal-Bench | – | 84.7% |
| SimpleBench | – | 69.0% |
| Remote Labor Index | – | 6.3% |
| APEX-Agents | – | 38.5% |
| FrontierCode | – | 43.0% |
| Epoch Capabilities Index | – | 159.1 |
| LMArena Text | 1456 | 1476 |
| LMArena Hard Prompts | 1487 | 1498 |
| LMArena Coding | 1520 | 1509 |
| LMArena WebDev | 1393 | 1458 |
| LMArena Vision | – | 1296 |
| LMArena Agent | – | 2.8 |
| AA Intelligence Index | – | 38.6 |
| IFBench | – | 75.8% |
| AA-LCR | – | 84.3% |
| MMMU-Pro | – | 79.9% |
| AA-Omniscience | – | 20.5 |
| Terminal-Bench Hard | – | 60.6% |
| GPQA Diamond (AA) | – | 93.5% |
| Humanity's Last Exam (AA) | – | 45.8% |
| SciCode (AA) | – | 55.8% |
| τ²-Bench Telecom (AA) | – | 93.9% |
| HiL-Bench | – | 39.7% |
| EQ-Bench 4 | – | 1315 |
| Kagi LLM Benchmark | – | 88.8% |
| SWE-bench Verified (bash only) | 71.4% | – |
Data as of 2026-09-13. Best configuration of each model; every score links to its source on the model pages.
Claude Sonnet 4.5 vs GPT-5.5: questions
- Is Claude Sonnet 4.5 better than GPT-5.5?
- GPT-5.5 leads on quality: 65.0 vs 57.9. The BenchLeader Index combines every independent quality benchmark; GPT-5.5 is ahead overall as of 2026-09-13, but check the category scores for your use.
- Is Claude Sonnet 4.5 better than GPT-5.5 for coding?
- GPT-5.5 scores higher in coding (57 vs 56 on the category index, where 50 is average).
- Which is cheaper, Claude Sonnet 4.5 or GPT-5.5?
- Claude Sonnet 4.5 is cheaper: $6.00 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, Claude Sonnet 4.5 or GPT-5.5?
- GPT-5.5 streams faster: 91 against 40 output tokens per second.
- Which has the larger context window?
- GPT-5.5 accepts more context: 1.1M against 1M tokens.