Model comparison
Grok 4 Fast vs Kimi K2 (Jul 2025)
Kimi K2 (Jul 2025) is the stronger model overall, scoring 41.2 to 39.4 on the Noometry Index.
Last verified . 23 shared benchmarks.
Summary
- They share 23 benchmarks with published results for both. Grok 4 Fast scores higher in 3 categories and Kimi K2 (Jul 2025) in 6 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in long context, where Grok 4 Fast leads 63.2 to 41.2.
- The biggest single-benchmark swing is Fiction.LiveBench: 94.4% for Grok 4 Fast and 66.7% for Kimi K2 (Jul 2025).
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.
Side by side
| Grok 4 Fast | Kimi K2 (Jul 2025) | |
|---|---|---|
| Provider | xAI | Moonshot AI |
| Noometry Index | 39.4 | 41.2 |
| Released | 2025-09-19 | 2025-07-12 |
| Weights | Proprietary | Open |
| Context window | — | 262K |
| Max output | — | 262K |
| Input $ / M tokens | — | $0.57 |
| Output $ / M tokens | — | $2.30 |
| Results tracked | 30 | 42 |
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Category by category
Coding Kimi K2 (Jul 2025) leads
Grok 4 Fast: 32.5 (#271), Kimi K2 (Jul 2025): 42.4 (#102)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| WeirdML | 42.9% | 42.8% |
| LMArena Coding | 1429 | 1399 |
| SWE-bench Verified (bash only) | — | 63.4% |
| Aider Polyglot | — | 59.1% |
| LMArena WebDev | 1159 | — |
| GSO | — | 4.9% |
| ALE-Bench | — | 597.5 |
Agentic & Tool Use Kimi K2 (Jul 2025) leads
Grok 4 Fast: 29.5 (#86), Kimi K2 (Jul 2025): 32.4 (#64)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Terminal-Bench | — | 35.7% |
| Berkeley Function Calling Leaderboard | — | 59.1% |
| τ²-bench Banking | 15.7% | — |
| Cybench | 30% | — |
| LMArena Search | 1171 | — |
| METR Time Horizons | — | 59.2% |
Reasoning Kimi K2 (Jul 2025) leads
Grok 4 Fast: 22.2 (#201), Kimi K2 (Jul 2025): 23.3 (#179)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Kagi LLM Benchmark | 66.1% | 64.4% |
| LMArena Hard Prompts | 1412 | 1384 |
| Epoch Capabilities Index | 144.2 | 146.01 |
| ForecastBench | 60.5 | 60.2 |
| ARC-AGI-2 | 5.3% | — |
| SimpleBench | — | 26.3% |
| ARC-AGI-1 | 48.5% | — |
| DTBench | 82.7% | — |
Math Kimi K2 (Jul 2025) leads
Grok 4 Fast: 38.9 (#123), Kimi K2 (Jul 2025): 42.7 (#83)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Math | 1419 | 1397 |
| Omni-MATH | — | 65.4% |
| FrontierMath (Feb 2025 set) | — | 21.4% |
| FrontierMath Tier 4 (v1) | — | 0% |
Knowledge Kimi K2 (Jul 2025) leads
Grok 4 Fast: 32.0 (#214), Kimi K2 (Jul 2025): 37.3 (#157)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Vectara Hallucination Rate | 19.7% | 17.9% |
| LMArena Expert | 1411 | 1365 |
| MMLU-Pro | — | 81.9% |
| Confabulations | — | 20.4% |
| GPQA (HELM) | — | 65.3% |
Multilingual Grok 4 Fast leads
Grok 4 Fast: 51.3 (#111), Kimi K2 (Jul 2025): 49.6 (#130)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1396 | 1372 |
| LMArena Chinese | 1457 | 1415 |
| LMArena French | 1431 | 1379 |
| LMArena German | 1383 | 1387 |
| LMArena Japanese | 1352 | 1349 |
| LMArena Korean | 1357 | 1325 |
| LMArena Russian | 1389 | 1385 |
| LMArena Spanish | 1415 | 1386 |
Instruction Following Grok 4 Fast leads
Grok 4 Fast: 73.2 (#121), Kimi K2 (Jul 2025): 71.1 (#156)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Instruction Following | 1387 | 1348 |
| IFEval | — | 85% |
Long Context Grok 4 Fast leads
Grok 4 Fast: 63.2 (#3), Kimi K2 (Jul 2025): 41.2 (#145)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| Fiction.LiveBench | 94.4% | 66.7% |
| LMArena Longer Query | 1415 | 1353 |
| CL-bench | — | 17.6% |
Writing & Preference Kimi K2 (Jul 2025) leads
Grok 4 Fast: 60.0 (#102), Kimi K2 (Jul 2025): 62.3 (#78)
| Benchmark | Grok 4 Fast | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1407 | 1380 |
| LMArena Creative Writing | 1387 | 1350 |
| LMArena Multi-Turn | 1414 | 1371 |
| Short-Story Creative Writing | — | 85.6% |
| EQ-Bench Creative Writing | — | 1666 |
| WildBench | — | 86.2% |
Frequently asked questions
Is Grok 4 Fast better than Kimi K2 (Jul 2025)?
Kimi K2 (Jul 2025) is the stronger model overall, scoring 41.2 to 39.4 on the Noometry Index.
Is Grok 4 Fast or Kimi K2 (Jul 2025) better for coding?
Kimi K2 (Jul 2025) scores higher on coding benchmarks: 42.4 versus 32.5 in the Noometry coding category.
How many benchmarks do Grok 4 Fast and Kimi K2 (Jul 2025) share?
23 benchmarks have published results for both models. Grok 4 Fast has 30 scored results on Noometry and Kimi K2 (Jul 2025) has 42.