# Grok 4.1 Fast vs Kimi K2 (Jul 2025)

> Grok 4.1 Fast and Kimi K2 (Jul 2025) score almost the same on the Noometry Index (40.9 vs 40.9), so choose on price, context window or the category you care about most.

- Canonical page: https://noometry.com/compare/grok-4-1-fast-vs-kimi-k2
- Last updated: 2026-10-10
- Shared benchmarks: 23

## Summary

- They share 23 benchmarks with published results for both. Grok 4.1 Fast scores higher in 5 categories and Kimi K2 (Jul 2025) in 4 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Grok 4.1 Fast leads 42.3 to 22.7.
- The biggest single-benchmark swing is SimpleBench: 56% for Grok 4.1 Fast and 26.3% for Kimi K2 (Jul 2025).
- Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $0.57 / $2.30 for Kimi K2 (Jul 2025).
- Kimi K2 (Jul 2025) accepts more context: 262K tokens versus 128K.
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.

## Snapshot

| | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Provider | xAI | Moonshot AI |
| Noometry Index | 40.9 | 40.9 |
| Rank | 131 | 134 |
| Context | 128K | 262K |
| Input $/M | $0.20 | $0.57 |
| Output $/M | $0.50 | $2.30 |
| Weights | Proprietary | Open |

## Coding

- Grok 4.1 Fast: 33.8 (#236)
- Kimi K2 (Jul 2025): 43.1 (#83)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Coding | 1411 | 1399 |
| ALE-Bench | 394.93 | 597.5 |
| SWE-bench Verified (bash only) | — | 63.4% |
| Aider Polyglot | — | 59.1% |
| LMArena WebDev | 1241 | — |
| GSO | — | 4.9% |
| WeirdML | — | 42.8% |

## Agentic & Tool Use

- Grok 4.1 Fast: 36.1 (#35)
- Kimi K2 (Jul 2025): 32.2 (#59)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Berkeley Function Calling Leaderboard | 69.6% | 59.1% |
| Terminal-Bench | — | 35.7% |
| τ²-bench Banking | 13.1% | — |
| LMArena Search | 1171 | — |
| METR Time Horizons | — | 59.2% |
| Vending-Bench 2 | 1,107 | — |

## Reasoning

- Grok 4.1 Fast: 42.3 (#45)
- Kimi K2 (Jul 2025): 22.7 (#173)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| SimpleBench | 56% | 26.3% |
| LMArena Hard Prompts | 1407 | 1384 |
| ForecastBench | 61 | 60.2 |
| Kagi LLM Benchmark | — | 64.4% |
| NYT Connections (extended) | 87.4% | — |
| DTBench | 87.7% | — |
| Epoch Capabilities Index | — | 146.02 |

## Math

- Grok 4.1 Fast: 30.9 (#201)
- Kimi K2 (Jul 2025): 40.1 (#81)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Math | 1408 | 1396 |
| MathArena Final-Answer Competitions | 60.9% | — |
| ProofBench | 4% | — |
| Omni-MATH | — | 65.4% |
| FrontierMath (Feb 2025 set) | — | 21.4% |
| FrontierMath Tier 4 (v1) | — | 0% |

## Knowledge

- Grok 4.1 Fast: 32.6 (#203)
- Kimi K2 (Jul 2025): 36.9 (#153)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Vectara Hallucination Rate | 17.8% | 17.9% |
| LMArena Expert | 1398 | 1363 |
| MMLU-Pro | — | 81.9% |
| Confabulations | — | 20.4% |
| GPQA (HELM) | — | 65.3% |

## Multimodal

- Grok 4.1 Fast: 36.3 (#71)
- Kimi K2 (Jul 2025): —

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Vision | 1201 | — |

## Multilingual

- Grok 4.1 Fast: 51.1 (#110)
- Kimi K2 (Jul 2025): 49.8 (#125)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1391 | 1372 |
| LMArena Chinese | 1441 | 1416 |
| LMArena French | 1416 | 1379 |
| LMArena German | 1404 | 1386 |
| LMArena Japanese | 1347 | 1349 |
| LMArena Korean | 1361 | 1324 |
| LMArena Russian | 1387 | 1384 |
| LMArena Spanish | 1411 | 1383 |

## Instruction Following

- Grok 4.1 Fast: 72.8 (#127)
- Kimi K2 (Jul 2025): 71.3 (#151)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Instruction Following | 1376 | 1347 |
| IFEval | — | 85% |

## Long Context

- Grok 4.1 Fast: 42.4 (#121)
- Kimi K2 (Jul 2025): 41.2 (#140)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Longer Query | 1390 | 1353 |
| Fiction.LiveBench | — | 66.7% |
| CL-bench | — | 17.6% |

## Writing & Preference

- Grok 4.1 Fast: 57.4 (#126)
- Kimi K2 (Jul 2025): 62.5 (#76)

| Benchmark | Grok 4.1 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1408 | 1380 |
| LMArena Creative Writing | 1394 | 1349 |
| EQ-Bench Creative Writing | 1327 | 1666 |
| LMArena Multi-Turn | 1389 | 1371 |
| Short-Story Creative Writing | — | 85.6% |
| WildBench | — | 86.2% |

## FAQ

### Is Grok 4.1 Fast better than Kimi K2 (Jul 2025)?

Grok 4.1 Fast and Kimi K2 (Jul 2025) score almost the same on the Noometry Index (40.9 vs 40.9), so choose on price, context window or the category you care about most.

### Which is cheaper, Grok 4.1 Fast or Kimi K2 (Jul 2025)?

Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; Kimi K2 (Jul 2025) lists at $0.57 and $2.30.

### Is Grok 4.1 Fast or Kimi K2 (Jul 2025) better for coding?

Kimi K2 (Jul 2025) scores higher on coding benchmarks: 43.1 versus 33.8 in the Noometry coding category.

### Which has the bigger context window?

Kimi K2 (Jul 2025) does, with 262K tokens against 128K.

### How many benchmarks do Grok 4.1 Fast and Kimi K2 (Jul 2025) share?

23 benchmarks have published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Kimi K2 (Jul 2025) has 42.