# Claude Opus 5.5 vs Kimi K2 (Jul 2025)

> Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 40.9 on the Noometry Index. Kimi K2 (Jul 2025) costs 8.0× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/claude-opus-5-5-vs-kimi-k2
- Last updated: 2026-10-10
- Shared benchmarks: 12

## Summary

- They share 12 benchmarks with published results for both. Claude Opus 5.5 scores higher in 9 categories and Kimi K2 (Jul 2025) in 0 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Claude Opus 5.5 leads 79.5 to 22.7.
- Kimi K2 (Jul 2025) is cheaper at $0.57 / $2.30 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
- Claude Opus 5.5 accepts more context: 1M tokens versus 262K.
- Kimi K2 (Jul 2025) has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Provider | Anthropic | Moonshot AI |
| Noometry Index | 68.5 | 40.9 |
| Rank | 3 | 134 |
| Context | 1M | 262K |
| Input $/M | $4 | $0.57 |
| Output $/M | $20 | $2.30 |
| Weights | Proprietary | Open |

## Coding

- Claude Opus 5.5: 71.4 (#1)
- Kimi K2 (Jul 2025): 43.1 (#83)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Coding | 1545 | 1399 |
| FrontierCode | 54.4% | — |
| SWE-bench Verified (bash only) | — | 63.4% |
| Aider Polyglot | — | 59.1% |
| CursorBench | 57.8% | — |
| LMArena WebDev | 1820 | — |
| FrontierSWE | 62.3% | — |
| SciCode | 66.9% | — |
| GSO | — | 4.9% |
| WeirdML | — | 42.8% |
| MirrorCode | 77.4% | — |
| ALE-Bench | — | 597.5 |

## Agentic & Tool Use

- Claude Opus 5.5: 45.3 (#13)
- Kimi K2 (Jul 2025): 32.2 (#59)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Terminal-Bench | — | 35.7% |
| APEX-Agents | 73.5% | — |
| Berkeley Function Calling Leaderboard | — | 59.1% |
| GDP.pdf | 30.6% | — |
| METR Time Horizons | — | 59.2% |

## Reasoning

- Claude Opus 5.5: 79.5 (#2)
- Kimi K2 (Jul 2025): 22.7 (#173)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Hard Prompts | 1545 | 1384 |
| ARC-AGI-2 | 92.5% | — |
| SimpleBench | — | 26.3% |
| Kagi LLM Benchmark | — | 64.4% |
| NYT Connections (extended) | 88.5% | — |
| ARC-AGI-1 | 97.5% | — |
| CritPt | 31.7% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| DTBench | 98.9% | — |
| LMCA | 68.2% | — |
| Epoch Capabilities Index | — | 146.02 |
| ForecastBench | — | 60.2 |

## Math

- Claude Opus 5.5: 92.4 (#2)
- Kimi K2 (Jul 2025): 40.1 (#81)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| Omni-MATH | — | 65.4% |
| LMArena Math | — | 1396 |
| FrontierMath (Feb 2025 set) | — | 21.4% |
| FrontierMath Tier 4 (v1) | — | 0% |

## Knowledge

- Claude Opus 5.5: 66.6 (#9)
- Kimi K2 (Jul 2025): 36.9 (#153)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Expert | 1564 | 1363 |
| GPQA Diamond | 90.6% | — |
| SimpleQA Verified | 72.2% | — |
| MMLU-Pro | — | 81.9% |
| Confabulations | — | 20.4% |
| Vectara Hallucination Rate | — | 17.9% |
| GPQA (HELM) | — | 65.3% |

## Multimodal

- Claude Opus 5.5: 56.5 (#2)
- Kimi K2 (Jul 2025): —

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| Furniture Assembly | 83.3% | — |

## Multilingual

- Claude Opus 5.5: 59.8 (#1)
- Kimi K2 (Jul 2025): 49.8 (#125)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Non-English | 1513 | 1372 |
| LMArena Chinese | 1572 | 1416 |
| LMArena Russian | 1532 | 1384 |
| LMArena French | — | 1379 |
| LMArena German | — | 1386 |
| LMArena Japanese | — | 1349 |
| LMArena Korean | — | 1324 |
| LMArena Spanish | — | 1383 |

## Instruction Following

- Claude Opus 5.5: 80.1 (#2)
- Kimi K2 (Jul 2025): 71.3 (#151)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Instruction Following | 1535 | 1347 |
| IFEval | — | 85% |

## Long Context

- Claude Opus 5.5: 47.3 (#18)
- Kimi K2 (Jul 2025): 41.2 (#140)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Longer Query | 1540 | 1353 |
| Fiction.LiveBench | — | 66.7% |
| CL-bench | — | 17.6% |

## Writing & Preference

- Claude Opus 5.5: 78.7 (#3)
- Kimi K2 (Jul 2025): 62.5 (#76)

| Benchmark | Claude Opus 5.5 | Kimi K2 (Jul 2025) |
|---|---|---|
| LMArena Text | 1518 | 1380 |
| LMArena Creative Writing | 1538 | 1349 |
| EQ-Bench Creative Writing | 2050 | 1666 |
| LMArena Multi-Turn | 1520 | 1371 |
| Short-Story Creative Writing | — | 85.6% |
| WildBench | — | 86.2% |

## FAQ

### Is Claude Opus 5.5 better than Kimi K2 (Jul 2025)?

Claude Opus 5.5 is the stronger model overall, scoring 68.5 to 40.9 on the Noometry Index. Kimi K2 (Jul 2025) costs 8.0× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.

### Which is cheaper, Claude Opus 5.5 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 Opus 5.5 lists at $4 and $20.

### Is Claude Opus 5.5 or Kimi K2 (Jul 2025) better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.4 versus 43.1 in the Noometry coding category.

### Which has the bigger context window?

Claude Opus 5.5 does, with 1M tokens against 262K.

### How many benchmarks do Claude Opus 5.5 and Kimi K2 (Jul 2025) share?

12 benchmarks have published results for both models. Claude Opus 5.5 has 35 scored results on Noometry and Kimi K2 (Jul 2025) has 42.