# GPT-5.5 Pro vs Grok 4 Fast

> GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 39.0 on the Noometry Index.

- Canonical page: https://noometry.com/compare/gpt-5-5-pro-vs-grok-4-fast
- Last updated: 2026-10-10
- Shared benchmarks: 4

## Summary

- They share 4 benchmarks with published results for both. GPT-5.5 Pro scores higher in 3 categories and Grok 4 Fast in 0 categories; 3 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where GPT-5.5 Pro leads 73.6 to 22.5.
- The biggest single-benchmark swing is ARC-AGI-2: 84.6% for GPT-5.5 Pro and 5.3% for Grok 4 Fast.

## Snapshot

| | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 64.3 | 39.0 |
| Rank | 7 | 164 |
| Context | 1.05M | — |
| Input $/M | $30 | — |
| Output $/M | $180 | — |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5 Pro: —
- Grok 4 Fast: 32.3 (#264)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| LMArena WebDev | — | 1160 |
| WeirdML | — | 42.9% |
| LMArena Coding | — | 1429 |

## Agentic & Tool Use

- GPT-5.5 Pro: —
- Grok 4 Fast: 29.3 (#80)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| τ²-bench Banking | — | 15.7% |
| Cybench | — | 30% |
| LMArena Search | — | 1171 |

## Reasoning

- GPT-5.5 Pro: 73.6 (#7)
- Grok 4 Fast: 22.5 (#179)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| ARC-AGI-2 | 84.6% | 5.3% |
| ARC-AGI-1 | 96.5% | 48.5% |
| DTBench | 96% | 82.7% |
| Epoch Capabilities Index | 162.45 | 144.21 |
| SimpleBench | 76.9% | — |
| Kagi LLM Benchmark | — | 66.1% |
| CritPt | 30.6% | — |
| Chess Puzzles | 64% | — |
| LMArena Hard Prompts | — | 1413 |
| LMCA | 53.9% | — |
| ForecastBench | — | 60.5 |

## Math

- GPT-5.5 Pro: 83.8 (#8)
- Grok 4 Fast: 36.1 (#126)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| FrontierMath (Tiers 1-3) | 87.7% | — |
| FrontierMath Tier 4 | 78% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| LMArena Math | — | 1419 |
| FrontierMath (Feb 2025 set) | 52.4% | — |
| FrontierMath Tier 4 (v1) | 39.6% | — |

## Knowledge

- GPT-5.5 Pro: 64.2 (#17)
- Grok 4 Fast: 31.5 (#211)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| GPQA Diamond | 93.9% | — |
| Vectara Hallucination Rate | — | 19.7% |
| LMArena Expert | — | 1411 |

## Multilingual

- GPT-5.5 Pro: —
- Grok 4 Fast: 51.5 (#106)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| LMArena Non-English | — | 1397 |
| LMArena Chinese | — | 1458 |
| LMArena French | — | 1433 |
| LMArena German | — | 1383 |
| LMArena Japanese | — | 1358 |
| LMArena Korean | — | 1359 |
| LMArena Russian | — | 1387 |
| LMArena Spanish | — | 1414 |

## Instruction Following

- GPT-5.5 Pro: —
- Grok 4 Fast: 73.4 (#116)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| LMArena Instruction Following | — | 1388 |

## Long Context

- GPT-5.5 Pro: —
- Grok 4 Fast: 63.2 (#3)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| Fiction.LiveBench | — | 94.4% |
| LMArena Longer Query | — | 1415 |

## Writing & Preference

- GPT-5.5 Pro: —
- Grok 4 Fast: 60.2 (#96)

| Benchmark | GPT-5.5 Pro | Grok 4 Fast |
|---|---|---|
| LMArena Text | — | 1407 |
| LMArena Creative Writing | — | 1388 |
| LMArena Multi-Turn | — | 1414 |

## FAQ

### Is GPT-5.5 Pro better than Grok 4 Fast?

GPT-5.5 Pro is the stronger model overall, scoring 64.3 to 39.0 on the Noometry Index.

### How many benchmarks do GPT-5.5 Pro and Grok 4 Fast share?

4 benchmarks have published results for both models. GPT-5.5 Pro has 14 scored results on Noometry and Grok 4 Fast has 30.