# Grok 4 Fast vs Mercury 2

> Grok 4 Fast and Mercury 2 score almost the same on the Noometry Index (39.4 vs 39.1), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/grok-4-fast-vs-mercury-2
- Last updated: 2026-10-10
- Shared benchmarks: 14

## Summary

- They share 14 benchmarks with published results for both. Grok 4 Fast scores higher in 4 categories and Mercury 2 in 3 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in long context, where Grok 4 Fast leads 63.2 to 40.5.
- The biggest single-benchmark swing is Vectara Hallucination Rate: 19.7% for Grok 4 Fast and 12.3% for Mercury 2.

## Snapshot

| | Grok 4 Fast | Mercury 2 |
|---|---|---|
| Provider | xAI | Inception |
| Noometry Index | 39.4 | 39.1 |
| Rank | 167 | 175 |
| Context | — | 128K |
| Input $/M | — | $0.25 |
| Output $/M | — | $0.75 |
| Weights | Proprietary | Proprietary |

## Coding

- Grok 4 Fast: 32.5 (#271)
- Mercury 2: 33.5 (#255)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena WebDev | 1159 | 1171 |
| WeirdML | 42.9% | 43.2% |
| LMArena Coding | 1429 | 1391 |
| SciCode | — | 38.7% |
| ALE-Bench | — | 785.58 |

## Agentic & Tool Use

- Grok 4 Fast: 29.5 (#86)
- Mercury 2: —

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| τ²-bench Banking | 15.7% | — |
| Cybench | 30% | — |
| LMArena Search | 1171 | — |

## Reasoning

- Grok 4 Fast: 22.2 (#201)
- Mercury 2: 23.8 (#170)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Hard Prompts | 1412 | 1362 |
| ARC-AGI-2 | 5.3% | — |
| Kagi LLM Benchmark | 66.1% | — |
| ARC-AGI-1 | 48.5% | — |
| CritPt | — | 0.8% |
| DTBench | 82.7% | — |
| Epoch Capabilities Index | 144.2 | — |
| ForecastBench | 60.5 | — |

## Math

- Grok 4 Fast: 38.9 (#123)
- Mercury 2: —

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Math | 1419 | — |

## Knowledge

- Grok 4 Fast: 32.0 (#214)
- Mercury 2: 36.2 (#172)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| Vectara Hallucination Rate | 19.7% | 12.3% |
| LMArena Expert | 1411 | 1358 |

## Multilingual

- Grok 4 Fast: 51.3 (#111)
- Mercury 2: 46.6 (#157)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Non-English | 1396 | 1331 |
| LMArena Chinese | 1457 | 1417 |
| LMArena Russian | 1389 | 1304 |
| LMArena French | 1431 | — |
| LMArena German | 1383 | — |
| LMArena Japanese | 1352 | — |
| LMArena Korean | 1357 | — |
| LMArena Spanish | 1415 | — |

## Instruction Following

- Grok 4 Fast: 73.2 (#121)
- Mercury 2: 70.2 (#165)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Instruction Following | 1387 | 1329 |

## Long Context

- Grok 4 Fast: 63.2 (#3)
- Mercury 2: 40.5 (#154)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Longer Query | 1415 | 1330 |
| Fiction.LiveBench | 94.4% | — |

## Writing & Preference

- Grok 4 Fast: 60.0 (#102)
- Mercury 2: 53.8 (#155)

| Benchmark | Grok 4 Fast | Mercury 2 |
|---|---|---|
| LMArena Text | 1407 | 1355 |
| LMArena Creative Writing | 1387 | 1289 |
| LMArena Multi-Turn | 1414 | 1358 |

## FAQ

### Is Grok 4 Fast better than Mercury 2?

Grok 4 Fast and Mercury 2 score almost the same on the Noometry Index (39.4 vs 39.1), so choose on price, context window or the category you care about most.

### Is Grok 4 Fast or Mercury 2 better for coding?

Mercury 2 scores higher on coding benchmarks: 33.5 versus 32.5 in the Noometry coding category.

### How many benchmarks do Grok 4 Fast and Mercury 2 share?

14 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Mercury 2 has 17.