# Claude Sonnet 4.5 vs Kimi K2 (Jul 2025)

> Claude Sonnet 4.5 is the stronger model overall, scoring 44.0 to 40.9 on the Noometry Index. Kimi K2 (Jul 2025) costs 6.0× less per token, which makes it the better buy when Claude Sonnet 4.5's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/claude-sonnet-4-5-vs-kimi-k2
- Last updated: 2026-10-10
- Shared benchmarks: 37

## Summary

- They share 37 benchmarks with published results for both. Claude Sonnet 4.5 scores higher in 8 categories and Kimi K2 (Jul 2025) in 1 category; 9 gaps are clear of the uncertainty.
- The widest gap is in knowledge, where Claude Sonnet 4.5 leads 48.4 to 36.9.
- The biggest single-benchmark swing is SimpleBench: 54.3% for Claude Sonnet 4.5 and 26.3% for Kimi K2 (Jul 2025).
- Kimi K2 (Jul 2025) is cheaper at $0.57 / $2.30 per million input/output tokens, against $3 / $15 for Claude Sonnet 4.5.
- Claude Sonnet 4.5 accepts more context: 1M tokens versus 262K.
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Provider | Anthropic | Moonshot AI |
| Noometry Index | 44.0 | 40.9 |
| Rank | 76 | 134 |
| Context | 1M | 262K |
| Input $/M | $3 | $0.57 |
| Output $/M | $15 | $2.30 |
| Weights | Proprietary | Open |

## Coding

- Claude Sonnet 4.5: 47.8 (#54)
- Kimi K2 (Jul 2025): 43.1 (#83)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| SWE-bench Verified (bash only) | 71.4% | 63.4% |
| GSO | 14.7% | 4.9% |
| WeirdML | 47.7% | 42.8% |
| LMArena Coding | 1489 | 1399 |
| ALE-Bench | 796.15 | 597.5 |
| SWE-bench Verified | 71.3% | — |
| Aider Polyglot | — | 59.1% |
| LMArena WebDev | 1393 | — |
| SWE-bench Multilingual | 67% | — |
| SciCode | 44.7% | — |
| AlgoTune | 1.52 | — |

## Agentic & Tool Use

- Claude Sonnet 4.5: 38.1 (#30)
- Kimi K2 (Jul 2025): 32.2 (#59)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Terminal-Bench | 46.5% | 35.7% |
| Berkeley Function Calling Leaderboard | 73.2% | 59.1% |
| METR Time Horizons | 67.4% | 59.2% |
| GDPval | 42.5% | — |
| Remote Labor Index | 2.1% | — |
| τ²-bench Airline | 72% | — |
| τ²-bench Banking | 25.3% | — |
| τ²-bench Retail | 72.4% | — |
| τ²-bench Telecom | 84.9% | — |
| Cybench | 60% | — |
| DeepResearch Bench | 52.6% | — |
| OSWorld | 62.9% | — |
| LMArena Search | 1159 | — |
| Vending-Bench 2 | 3,839 | — |

## Reasoning

- Claude Sonnet 4.5: 26.9 (#113)
- Kimi K2 (Jul 2025): 22.7 (#173)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| SimpleBench | 54.3% | 26.3% |
| Kagi LLM Benchmark | 57.9% | 64.4% |
| LMArena Hard Prompts | 1462 | 1384 |
| Epoch Capabilities Index | 146.84 | 146.02 |
| ForecastBench | 61.9 | 60.2 |
| ARC-AGI-2 | 13.6% | — |
| NYT Connections (extended) | 37.3% | — |
| ARC-AGI-1 | 63.7% | — |
| CritPt | 1.1% | — |
| Chess Puzzles | 12% | — |
| EnigmaEval | 6% | — |
| EBR-Bench | 2.4% | — |
| Mystery Game Puzzles | 17% | — |
| DTBench | 83.2% | — |
| LMCA | 38.8% | — |

## Math

- Claude Sonnet 4.5: 31.9 (#190)
- Kimi K2 (Jul 2025): 40.1 (#81)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Omni-MATH | 55.3% | 65.4% |
| LMArena Math | 1448 | 1396 |
| FrontierMath (Feb 2025 set) | 15.2% | 21.4% |
| FrontierMath Tier 4 (v1) | 4.2% | 0% |
| FrontierMath (Tiers 1-3) | 23.9% | — |
| FrontierMath Tier 4 | 2.4% | — |
| OTIS Mock AIME 2024-2025 | 77.8% | — |
| ProofBench | 19% | — |
| MATH Level 5 | 97.7% | — |

## Knowledge

- Claude Sonnet 4.5: 48.4 (#70)
- Kimi K2 (Jul 2025): 36.9 (#153)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| MMLU-Pro | 86.9% | 81.9% |
| Vectara Hallucination Rate | 12% | 17.9% |
| GPQA (HELM) | 68.6% | 65.3% |
| LMArena Expert | 1483 | 1363 |
| GPQA Diamond | 82.3% | — |
| Humanity's Last Exam | 13.7% | — |
| SimpleQA Verified | 30.7% | — |
| Confabulations | — | 20.4% |

## Multimodal

- Claude Sonnet 4.5: 34.1 (#84)
- Kimi K2 (Jul 2025): —

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| VPCT | 39.8% | — |
| LMArena Document | 1450 | — |

## Multilingual

- Claude Sonnet 4.5: 53.6 (#65)
- Kimi K2 (Jul 2025): 49.8 (#125)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1425 | 1372 |
| LMArena Chinese | 1459 | 1416 |
| LMArena French | 1459 | 1379 |
| LMArena German | 1427 | 1386 |
| LMArena Japanese | 1390 | 1349 |
| LMArena Korean | 1403 | 1324 |
| LMArena Russian | 1436 | 1384 |
| LMArena Spanish | 1457 | 1383 |

## Instruction Following

- Claude Sonnet 4.5: 75.2 (#74)
- Kimi K2 (Jul 2025): 71.3 (#151)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| IFEval | 85% | 85% |
| LMArena Instruction Following | 1459 | 1347 |

## Long Context

- Claude Sonnet 4.5: 45.2 (#45)
- Kimi K2 (Jul 2025): 41.2 (#140)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Longer Query | 1476 | 1353 |
| Fiction.LiveBench | — | 66.7% |
| CL-bench | — | 17.6% |

## Writing & Preference

- Claude Sonnet 4.5: 66.7 (#33)
- Kimi K2 (Jul 2025): 62.5 (#76)

| Benchmark | Claude Sonnet 4.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1439 | 1380 |
| LMArena Creative Writing | 1442 | 1349 |
| EQ-Bench Creative Writing | 1678 | 1666 |
| WildBench | 85.4% | 86.2% |
| LMArena Multi-Turn | 1465 | 1371 |
| Short-Story Creative Writing | — | 85.6% |

## FAQ

### Is Claude Sonnet 4.5 better than Kimi K2 (Jul 2025)?

Claude Sonnet 4.5 is the stronger model overall, scoring 44.0 to 40.9 on the Noometry Index. Kimi K2 (Jul 2025) costs 6.0× less per token, which makes it the better buy when Claude Sonnet 4.5's lead doesn't matter for your workload.

### Which is cheaper, Claude Sonnet 4.5 or Kimi K2 (Jul 2025)?

Kimi K2 (Jul 2025) is cheaper. It lists at $0.57 per million input tokens and $2.30 per million output tokens; Claude Sonnet 4.5 lists at $3 and $15.

### Is Claude Sonnet 4.5 or Kimi K2 (Jul 2025) better for coding?

Claude Sonnet 4.5 scores higher on coding benchmarks: 47.8 versus 43.1 in the Noometry coding category.

### Which has the bigger context window?

Claude Sonnet 4.5 does, with 1M tokens against 262K.

### How many benchmarks do Claude Sonnet 4.5 and Kimi K2 (Jul 2025) share?

37 benchmarks have published results for both models. Claude Sonnet 4.5 has 73 scored results on Noometry and Kimi K2 (Jul 2025) has 42.