# Grok 4.5 vs Grok 4 Fast

> Grok 4.5 is the stronger model overall, scoring 55.0 to 39.0 on the Noometry Index.

- Canonical page: https://noometry.com/compare/grok-4-5-vs-grok-4-fast
- Last updated: 2026-10-10
- Shared benchmarks: 26

## Summary

- They share 26 benchmarks with published results for both. Grok 4.5 scores higher in 8 categories and Grok 4 Fast in 1 category; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Grok 4.5 leads 56.0 to 22.5.
- The biggest single-benchmark swing is ARC-AGI-2: 52.6% for Grok 4.5 and 5.3% for Grok 4 Fast.

## Snapshot

| | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| Provider | xAI | xAI |
| Noometry Index | 55.0 | 39.0 |
| Rank | 22 | 164 |
| Context | 500K | — |
| Input $/M | $2 | — |
| Output $/M | $6 | — |
| Weights | Proprietary | Proprietary |

## Coding

- Grok 4.5: 51.7 (#34)
- Grok 4 Fast: 32.3 (#264)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena WebDev | 1552 | 1160 |
| WeirdML | 46.4% | 42.9% |
| LMArena Coding | 1473 | 1429 |
| DeepSWE | 53.8% | — |
| FrontierCode | 42.4% | — |
| SciCode | 54.1% | — |
| ALE-Bench | 1,309 | — |

## Agentic & Tool Use

- Grok 4.5: 44.4 (#15)
- Grok 4 Fast: 29.3 (#80)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| τ²-bench Banking | 47.9% | 15.7% |
| LMArena Search | 1213 | 1171 |
| APEX-Agents | 56.2% | — |
| Cybench | — | 30% |
| PostTrainBench | 23.4% | — |
| GBAEval | 65.4% | — |
| GDP.pdf | 14% | — |
| Vending-Bench 2 | 3,887 | — |

## Reasoning

- Grok 4.5: 56.0 (#23)
- Grok 4 Fast: 22.5 (#179)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| ARC-AGI-2 | 52.6% | 5.3% |
| Kagi LLM Benchmark | 83.5% | 66.1% |
| ARC-AGI-1 | 87.2% | 48.5% |
| LMArena Hard Prompts | 1462 | 1413 |
| DTBench | 96.5% | 82.7% |
| Epoch Capabilities Index | 154.02 | 144.21 |
| SimpleBench | 70% | — |
| NYT Connections (extended) | 79.9% | — |
| CritPt | 15.4% | — |
| Chess Puzzles | 36% | — |
| LMCA | 45.2% | — |
| Surface Evolver Bench | 74.4% | — |
| ForecastBench | — | 60.5 |

## Math

- Grok 4.5: 60.7 (#29)
- Grok 4 Fast: 36.1 (#126)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Math | 1457 | 1419 |
| FrontierMath (Tiers 1-3) | 57.2% | — |
| FrontierMath Tier 4 | 24.4% | — |
| OTIS Mock AIME 2024-2025 | 97.8% | — |
| ProofBench | 31% | — |

## Knowledge

- Grok 4.5: 62.3 (#21)
- Grok 4 Fast: 31.5 (#211)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Expert | 1466 | 1411 |
| GPQA Diamond | 93.4% | — |
| SimpleQA Verified | 48.3% | — |
| Vectara Hallucination Rate | — | 19.7% |

## Multimodal

- Grok 4.5: 37.8 (#63)
- Grok 4 Fast: —

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Vision | 1287 | — |
| Blueprint-Bench 2 | 27.3% | — |
| Furniture Assembly | 22.5% | — |
| LMArena Document | 1452 | — |

## Multilingual

- Grok 4.5: 54.5 (#43)
- Grok 4 Fast: 51.5 (#106)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Non-English | 1439 | 1397 |
| LMArena Chinese | 1497 | 1458 |
| LMArena French | 1458 | 1433 |
| LMArena German | 1448 | 1383 |
| LMArena Japanese | 1425 | 1358 |
| LMArena Korean | 1402 | 1359 |
| LMArena Russian | 1447 | 1387 |
| LMArena Spanish | 1452 | 1414 |

## Instruction Following

- Grok 4.5: 76.3 (#45)
- Grok 4 Fast: 73.4 (#116)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Instruction Following | 1446 | 1388 |

## Long Context

- Grok 4.5: 44.8 (#54)
- Grok 4 Fast: 63.2 (#3)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Longer Query | 1463 | 1415 |
| Fiction.LiveBench | — | 94.4% |

## Writing & Preference

- Grok 4.5: 65.9 (#40)
- Grok 4 Fast: 60.2 (#96)

| Benchmark | Grok 4.5 | Grok 4 Fast |
|---|---|---|
| LMArena Text | 1448 | 1407 |
| LMArena Creative Writing | 1442 | 1388 |
| LMArena Multi-Turn | 1457 | 1414 |
| EQ-Bench Creative Writing | 1579 | — |

## FAQ

### Is Grok 4.5 better than Grok 4 Fast?

Grok 4.5 is the stronger model overall, scoring 55.0 to 39.0 on the Noometry Index.

### Is Grok 4.5 or Grok 4 Fast better for coding?

Grok 4.5 scores higher on coding benchmarks: 51.7 versus 32.3 in the Noometry coding category.

### How many benchmarks do Grok 4.5 and Grok 4 Fast share?

26 benchmarks have published results for both models. Grok 4.5 has 52 scored results on Noometry and Grok 4 Fast has 30.