GPT-5.5 Instant vs Grok 4.5
GPT-5.5 Instant 
Grok 4.5 Verdict
- Grok 4.5 leads on quality: 63.5 vs 60.5.
- GPT-5.5 Instant is stronger in agents & tools, coding, human preference, instruction following, maths.
- Grok 4.5 is stronger in composite, knowledge, long context, multimodal, reasoning.
- Grok 4.5 is 3.8× cheaper ($3.00 vs $11.25 per 1M blended).
- GPT-5.5 Instant streams 2.5× faster (129 vs 52 tokens per second).
| Metric | GPT-5.5 Instant | Grok 4.5 |
|---|---|---|
| BenchLeader Index | 60.5 | 63.5 |
| Agents & tools score | 70.7 | 58.6 |
| Coding score | 61.1 | 59.8 |
| Composite score | 62.9 | 66.2 |
| Human preference score | 67.5 | 67.2 |
| Instruction following score | 69.8 | – |
| Knowledge score | 69.4 | 76.2 |
| Long context score | 61.4 | 66.2 |
| Maths score | 42.5 | – |
| Multimodal score | 59.7 | 64.9 |
| Reasoning score | 62.6 | 69.2 |
| Blended price $/M | $11.25 | $3.00 |
| Output speed | 129 tok/s | 52 tok/s |
| Time to first answer | 16.8 s | 13.6 s |
| Context window | 400k | 500k |
| GPQA Diamond | 82.5% | – |
| FrontierMath Tiers 1–3 | 26.3% | – |
| FrontierMath Tier 4 | 2.4% | – |
| OTIS Mock AIME | 68.1% | – |
| SimpleBench | – | 70.0% |
| SciCode | 48.6% | – |
| WeirdML | – | 46.4% |
| APEX-Agents | – | 34.2% |
| FrontierCode | – | 42.4% |
| Epoch Capabilities Index | 142.5 | 153.9 |
| LMArena Text | 1474 | 1471 |
| LMArena Hard Prompts | 1491 | 1495 |
| LMArena Coding | 1514 | 1523 |
| LMArena WebDev | – | 1556 |
| LMArena Vision | 1251 | 1291 |
| LMArena Agent | – | 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 | 26.8 | 39.1 |
| IFBench | 71.5% | – |
| AA-LCR | 70.0% | 79.3% |
| MMMU-Pro | – | 80.4% |
| AA-Omniscience | 11.2 | 25.3 |
| Terminal-Bench Hard | 42.4% | – |
| GPQA Diamond (AA) | 84.7% | 93.1% |
| Humanity's Last Exam (AA) | 21.6% | 42.7% |
| SciCode (AA) | 52.5% | 55.0% |
| τ²-Bench Telecom (AA) | 49.4% | – |
| Kagi LLM Benchmark | – | 83.5% |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
GPT-5.5 Instant vs Grok 4.5: questions
- Is GPT-5.5 Instant better than Grok 4.5?
- Grok 4.5 leads on quality: 63.5 vs 60.5. The BenchLeader Index combines every independent quality benchmark; Grok 4.5 is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.5 Instant better than Grok 4.5 for coding?
- GPT-5.5 Instant scores higher in coding (61 vs 60 on the category index, where 50 is average).
- Is GPT-5.5 Instant better than Grok 4.5 for agentic tasks?
- GPT-5.5 Instant scores higher in agentic tasks (71 vs 59 on the category index, where 50 is average).
- Which is cheaper, GPT-5.5 Instant or Grok 4.5?
- Grok 4.5 is cheaper: $3.00 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.5 Instant or Grok 4.5?
- GPT-5.5 Instant streams faster: 129 against 52 output tokens per second.
- Which has the larger context window?
- Grok 4.5 accepts more context: 500k against 400k tokens.