GPT-5.5 vs Grok 4.5
GPT-5.5 
Grok 4.5 Verdict
- GPT-5.5 leads on quality: 66.6 vs 63.4.
- GPT-5.5 is stronger in agents & tools, composite, human preference, instruction following, long context, multimodal, reasoning.
- Grok 4.5 is stronger in coding, knowledge.
- Grok 4.5 is 3.8× cheaper ($3.00 vs $11.25 per 1M blended).
- GPT-5.5 streams 1.6× faster (88 vs 56 tokens per second).
| Metric | GPT-5.5 | Grok 4.5 |
|---|---|---|
| BenchLeader Index | 66.6 | 63.4 |
| Agents & tools score | 68.4 | 58.6 |
| Coding score | 57.3 | 59.9 |
| Composite score | 77.7 | 66.0 |
| Human preference score | 67.6 | 66.9 |
| Instruction following score | 73.3 | – |
| Knowledge score | 73.7 | 76.0 |
| Long context score | 68.8 | 66.2 |
| Multimodal score | 64.9 | 64.8 |
| Reasoning score | 69.7 | 68.9 |
| Blended price $/M | $11.25 | $3.00 |
| Output speed | 88 tok/s | 56 tok/s |
| Time to first answer | 62.3 s | 12.7 s |
| Context window | 1.1M | 500k |
| Terminal-Bench | 84.7% | – |
| SimpleBench | 69.0% | 70.0% |
| Remote Labor Index | 6.3% | – |
| WeirdML | – | 46.4% |
| APEX-Agents | 38.5% | 34.2% |
| FrontierCode | 43.0% | 42.4% |
| Epoch Capabilities Index | 159.1 | 153.9 |
| LMArena Text | 1477 | 1471 |
| LMArena Hard Prompts | 1498 | 1495 |
| LMArena Coding | 1509 | 1523 |
| LMArena WebDev | 1458 | 1556 |
| LMArena Vision | 1296 | 1291 |
| LMArena Agent | 3 | 3.9 |
| LiveBench | – | 75.8% |
| LiveBench Reasoning | – | 87.2% |
| LiveBench Coding | – | 68.6% |
| LiveBench Agentic Coding | – | 56.5% |
| LiveBench Mathematics | – | 90.8% |
| LiveBench Data Analysis | – | 73.0% |
| LiveBench Language | – | 82.8% |
| AA Intelligence Index | 38.6 | 39.1 |
| IFBench | 75.8% | – |
| AA-LCR | 84.3% | 79.3% |
| MMMU-Pro | 79.9% | 80.4% |
| AA-Omniscience | 20.5 | 25.3 |
| Terminal-Bench Hard | 60.6% | – |
| GPQA Diamond (AA) | 93.5% | 93.1% |
| Humanity's Last Exam (AA) | 45.8% | 42.7% |
| SciCode (AA) | 55.8% | 55.0% |
| τ²-Bench Telecom (AA) | 93.9% | – |
| HiL-Bench | 39.7% | – |
| EQ-Bench 4 | 1315 | – |
| Kagi LLM Benchmark | 88.8% | 83.5% |
Data as of 2026-09-09. Best configuration of each model; every score links to its source on the model pages.