# Grok 4.1 Fast vs Grok 4.5

> Grok 4.5 is the stronger model overall, scoring 55.0 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 11× less per token, which makes it the better buy when Grok 4.5's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/grok-4-1-fast-vs-grok-4-5
- Last updated: 2026-10-12
- Shared benchmarks: 28

## Summary

- They share 28 benchmarks with published results for both. Grok 4.1 Fast scores higher in 0 categories and Grok 4.5 in 10 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in knowledge, where Grok 4.5 leads 62.3 to 33.1.
- The biggest single-benchmark swing is τ²-bench Banking: 13.1% for Grok 4.1 Fast and 47.9% for Grok 4.5.
- Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $2 / $6 for Grok 4.5.
- Grok 4.5 accepts more context: 500K tokens versus 128K.

## Snapshot

| | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| Provider | xAI | xAI |
| Noometry Index | 41.4 | 55.0 |
| Rank | 136 | 25 |
| Context | 128K | 500K |
| Input $/M | $0.20 | $2 |
| Output $/M | $0.50 | $6 |
| Weights | Proprietary | Proprietary |

## Coding

- Grok 4.1 Fast: 34.1 (#245)
- Grok 4.5: 52.2 (#35)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena WebDev | 1242 | 1553 |
| LMArena Coding | 1411 | 1474 |
| ALE-Bench | 394.93 | 1,309 |
| DeepSWE | — | 53.8% |
| FrontierCode | — | 42.4% |
| SciCode | — | 54.1% |
| WeirdML | — | 46.4% |

## Agentic & Tool Use

- Grok 4.1 Fast: 36.3 (#39)
- Grok 4.5: 44.4 (#17)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| τ²-bench Banking | 13.1% | 47.9% |
| LMArena Search | 1171 | 1213 |
| Vending-Bench 2 | 1,107 | 3,887 |
| APEX-Agents | — | 56.2% |
| Berkeley Function Calling Leaderboard | 69.6% | — |
| PostTrainBench | — | 23.4% |
| GBAEval | — | 65.4% |
| GDP.pdf | — | 14% |

## Reasoning

- Grok 4.1 Fast: 43.4 (#49)
- Grok 4.5: 56.1 (#25)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| SimpleBench | 56% | 70% |
| NYT Connections (extended) | 87.4% | 79.9% |
| LMArena Hard Prompts | 1407 | 1462 |
| DTBench | 87.7% | 96.5% |
| ARC-AGI-2 | — | 52.6% |
| Kagi LLM Benchmark | — | 83.5% |
| ARC-AGI-1 | — | 87.2% |
| CritPt | — | 15.4% |
| Chess Puzzles | — | 36% |
| LMCA | — | 45.2% |
| Surface Evolver Bench | — | 74.4% |
| Epoch Capabilities Index | — | 153.92 |
| ForecastBench | 61 | — |

## Math

- Grok 4.1 Fast: 31.9 (#221)
- Grok 4.5: 60.9 (#35)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| ProofBench | 4% | 31% |
| LMArena Math | 1408 | 1459 |
| FrontierMath (Tiers 1-3) | — | 57.2% |
| FrontierMath Tier 4 | — | 24.4% |
| MathArena Final-Answer Competitions | 60.9% | — |
| OTIS Mock AIME 2024-2025 | — | 97.8% |

## Knowledge

- Grok 4.1 Fast: 33.1 (#207)
- Grok 4.5: 62.3 (#24)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Expert | 1399 | 1466 |
| GPQA Diamond | — | 93.4% |
| SimpleQA Verified | — | 48.3% |
| Vectara Hallucination Rate | 17.8% | — |

## Multimodal

- Grok 4.1 Fast: 37.0 (#76)
- Grok 4.5: 37.6 (#72)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Vision | 1201 | 1288 |
| Blueprint-Bench 2 | — | 27.3% |
| Furniture Assembly | — | 22.5% |
| LMArena Document | — | 1452 |

## Multilingual

- Grok 4.1 Fast: 51.0 (#114)
- Grok 4.5: 54.4 (#42)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Non-English | 1391 | 1440 |
| LMArena Chinese | 1441 | 1496 |
| LMArena French | 1415 | 1456 |
| LMArena German | 1404 | 1446 |
| LMArena Japanese | 1349 | 1428 |
| LMArena Korean | 1361 | 1404 |
| LMArena Russian | 1387 | 1448 |
| LMArena Spanish | 1413 | 1450 |

## Instruction Following

- Grok 4.1 Fast: 72.7 (#133)
- Grok 4.5: 76.0 (#48)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Instruction Following | 1376 | 1446 |

## Long Context

- Grok 4.1 Fast: 42.4 (#126)
- Grok 4.5: 44.8 (#56)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Longer Query | 1390 | 1463 |

## Writing & Preference

- Grok 4.1 Fast: 57.2 (#131)
- Grok 4.5: 65.8 (#42)

| Benchmark | Grok 4.1 Fast | Grok 4.5 |
|---|---|---|
| LMArena Text | 1408 | 1448 |
| LMArena Creative Writing | 1394 | 1442 |
| EQ-Bench Creative Writing | 1327 | 1579 |
| LMArena Multi-Turn | 1389 | 1456 |

## FAQ

### Is Grok 4.1 Fast better than Grok 4.5?

Grok 4.5 is the stronger model overall, scoring 55.0 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 11× less per token, which makes it the better buy when Grok 4.5's lead doesn't matter for your workload.

### Which is cheaper, Grok 4.1 Fast or Grok 4.5?

Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; Grok 4.5 lists at $2 and $6.

### Is Grok 4.1 Fast or Grok 4.5 better for coding?

Grok 4.5 scores higher on coding benchmarks: 52.2 versus 34.1 in the Noometry coding category.

### Which has the bigger context window?

Grok 4.5 does, with 500K tokens against 128K.

### How many benchmarks do Grok 4.1 Fast and Grok 4.5 share?

28 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Grok 4.5 has 52.