# GPT-5.5 vs Grok 4.1 Fast

> GPT-5.5 is the stronger model overall, scoring 63.4 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 41× less per token, which makes it the better buy when GPT-5.5's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-5-5-vs-grok-4-1-fast
- Last updated: 2026-10-10
- Shared benchmarks: 31

## Summary

- They share 31 benchmarks with published results for both. GPT-5.5 scores higher in 10 categories and Grok 4.1 Fast in 0 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in math, where GPT-5.5 leads 81.5 to 30.9.
- The biggest single-benchmark swing is ProofBench: 50% for GPT-5.5 and 4% for Grok 4.1 Fast.
- Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $5 / $30 for GPT-5.5.
- GPT-5.5 accepts more context: 1.05M tokens versus 128K.

## Snapshot

| | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 63.4 | 40.9 |
| Rank | 8 | 131 |
| Context | 1.05M | 128K |
| Input $/M | $5 | $0.20 |
| Output $/M | $30 | $0.50 |
| Weights | Proprietary | Proprietary |

## Coding

- GPT-5.5: 58.3 (#13)
- Grok 4.1 Fast: 33.8 (#236)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena WebDev | 1512 | 1241 |
| LMArena Coding | 1494 | 1411 |
| ALE-Bench | 1,943 | 394.93 |
| SWE-bench Verified | 80.6% | — |
| DeepSWE | 67% | — |
| FrontierCode | 43% | — |
| SciCode | 56.1% | — |
| GSO | 40.2% | — |
| WeirdML | 84.9% | — |
| MirrorCode | 10% | — |

## Agentic & Tool Use

- GPT-5.5: 50.7 (#6)
- Grok 4.1 Fast: 36.1 (#35)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| τ²-bench Banking | 44.6% | 13.1% |
| LMArena Search | 1242 | 1171 |
| Vending-Bench 2 | 7,524 | 1,107 |
| Terminal-Bench | 84.7% | — |
| APEX-Agents | 55.1% | — |
| Berkeley Function Calling Leaderboard | — | 69.6% |
| OSWorld 2.0 | 13% | — |
| Remote Labor Index | 6.3% | — |
| DeepResearch Bench | 54% | — |
| PostTrainBench | 27.2% | — |
| ExploitBench | 47.4% | — |
| GBAEval | 53.2% | — |
| GDP.pdf | 26% | — |

## Reasoning

- GPT-5.5: 72.7 (#8)
- Grok 4.1 Fast: 42.3 (#45)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| SimpleBench | 69% | 56% |
| NYT Connections (extended) | 96.2% | 87.4% |
| LMArena Hard Prompts | 1489 | 1407 |
| DTBench | 96% | 87.7% |
| ForecastBench | 60.6 | 61 |
| ARC-AGI-2 | 85% | — |
| Kagi LLM Benchmark | 88.8% | — |
| ARC-AGI-1 | 95% | — |
| CritPt | 27.1% | — |
| Chess Puzzles | 54% | — |
| EBR-Bench | 34.3% | — |
| Mystery Game Puzzles | 56% | — |
| LMCA | 54.3% | — |
| Surface Evolver Bench | 88.1% | — |
| Bench to the Future 3 | 0.14 | — |
| Epoch Capabilities Index | 159.25 | — |

## Math

- GPT-5.5: 81.5 (#9)
- Grok 4.1 Fast: 30.9 (#201)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| MathArena Final-Answer Competitions | 94.3% | 60.9% |
| ProofBench | 50% | 4% |
| LMArena Math | 1486 | 1408 |
| FrontierMath (Tiers 1-3) | 85.3% | — |
| FrontierMath Tier 4 | 72.5% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath (Feb 2025 set) | 51.7% | — |
| FrontierMath Erdős | 0% | — |
| FrontierMath Tier 4 (v1) | 35.4% | — |

## Knowledge

- GPT-5.5: 64.4 (#14)
- Grok 4.1 Fast: 32.6 (#203)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| Vectara Hallucination Rate | 9.3% | 17.8% |
| LMArena Expert | 1508 | 1398 |
| GPQA Diamond | 94% | — |
| SimpleQA Verified | 63% | — |

## Multimodal

- GPT-5.5: 47.1 (#11)
- Grok 4.1 Fast: 36.3 (#71)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Vision | 1297 | 1201 |
| Blueprint-Bench 2 | 36.2% | — |
| Furniture Assembly | 44.2% | — |
| LMArena Document | 1486 | — |

## Multilingual

- GPT-5.5: 56.5 (#19)
- Grok 4.1 Fast: 51.1 (#110)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Non-English | 1467 | 1391 |
| LMArena Chinese | 1535 | 1441 |
| LMArena French | 1486 | 1416 |
| LMArena German | 1478 | 1404 |
| LMArena Japanese | 1498 | 1347 |
| LMArena Korean | 1461 | 1361 |
| LMArena Russian | 1473 | 1387 |
| LMArena Spanish | 1469 | 1411 |

## Instruction Following

- GPT-5.5: 77.7 (#18)
- Grok 4.1 Fast: 72.8 (#127)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Instruction Following | 1479 | 1376 |

## Long Context

- GPT-5.5: 48.3 (#12)
- Grok 4.1 Fast: 42.4 (#121)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Longer Query | 1484 | 1390 |
| CL-bench Life | 22.2% | — |

## Writing & Preference

- GPT-5.5: 72.8 (#13)
- Grok 4.1 Fast: 57.4 (#126)

| Benchmark | GPT-5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Text | 1471 | 1408 |
| LMArena Creative Writing | 1455 | 1394 |
| EQ-Bench Creative Writing | 1844 | 1327 |
| LMArena Multi-Turn | 1477 | 1389 |
| EQ-Bench 4 | 1315 | — |

## FAQ

### Is GPT-5.5 better than Grok 4.1 Fast?

GPT-5.5 is the stronger model overall, scoring 63.4 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 41× less per token, which makes it the better buy when GPT-5.5's lead doesn't matter for your workload.

### Which is cheaper, GPT-5.5 or Grok 4.1 Fast?

Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; GPT-5.5 lists at $5 and $30.

### Is GPT-5.5 or Grok 4.1 Fast better for coding?

GPT-5.5 scores higher on coding benchmarks: 58.3 versus 33.8 in the Noometry coding category.

### Which has the bigger context window?

GPT-5.5 does, with 1.05M tokens against 128K.

### How many benchmarks do GPT-5.5 and Grok 4.1 Fast share?

31 benchmarks have published results for both models. GPT-5.5 has 71 scored results on Noometry and Grok 4.1 Fast has 32.