# Claude Sonnet 5.5 vs Kimi K3

> Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 59.5 on the Noometry Index.

- Canonical page: https://noometry.com/compare/claude-sonnet-5-5-vs-kimi-k3
- Last updated: 2026-10-10
- Shared benchmarks: 29

## Summary

- They share 29 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 7 categories and Kimi K3 in 3 categories; 7 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5.5 leads 87.9 to 74.2.
- The biggest single-benchmark swing is FrontierMath Tier 4: 80.5% for Claude Sonnet 5.5 and 39% for Kimi K3.
- Claude Sonnet 5.5 is cheaper at $2 / $10 per million input/output tokens, against $3 / $15 for Kimi K3.
- Kimi K3 accepts more context: 1.05M tokens versus 1M.
- Kimi K3 has downloadable open weights; the other is API-only.

## Snapshot

| | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| Provider | Anthropic | Moonshot AI |
| Noometry Index | 61.9 | 59.5 |
| Rank | 10 | 15 |
| Context | 1M | 1.05M |
| Input $/M | $2 | $3 |
| Output $/M | $10 | $15 |
| Weights | Proprietary | Open |

## Coding

- Claude Sonnet 5.5: 67.3 (#6)
- Kimi K3: 61.0 (#10)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| FrontierCode | 52.1% | 44.2% |
| LMArena WebDev | 1774 | 1654 |
| FrontierSWE | 61.9% | 25.9% |
| SciCode | 61% | 59.5% |
| LMArena Coding | 1513 | 1508 |
| ALE-Bench | 1,819 | 1,524 |
| DeepSWE | — | 68.5% |
| CursorBench | 55.5% | — |
| WeirdML | — | 82.6% |

## Agentic & Tool Use

- Claude Sonnet 5.5: 45.0 (#16)
- Kimi K3: 41.8 (#20)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| APEX-Agents | 75.5% | 50.6% |
| τ²-bench Banking | — | 37.1% |
| PostTrainBench | — | 32% |
| GBAEval | — | 48.3% |
| GDP.pdf | — | 19% |
| Vending-Bench 2 | — | 5,165 |

## Reasoning

- Claude Sonnet 5.5: 54.0 (#28)
- Kimi K3: 63.0 (#17)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| NYT Connections (extended) | 80.5% | 93.6% |
| CritPt | 31.4% | 23.4% |
| LMArena Hard Prompts | 1495 | 1496 |
| Mystery Game Puzzles | 65% | 26% |
| Epoch Capabilities Index | 165.03 | 157.45 |
| ARC-AGI-2 | — | 60.4% |
| SimpleBench | — | 60.7% |
| ARC-AGI-1 | — | 94.5% |
| Chess Puzzles | — | 39% |
| DTBench | — | 91.2% |
| LMCA | — | 52.7% |
| Surface Evolver Bench | — | 95% |
| ForecastBench | — | 61.1 |

## Math

- Claude Sonnet 5.5: 87.9 (#6)
- Kimi K3: 74.2 (#16)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| FrontierMath (Tiers 1-3) | 88.8% | 72.2% |
| FrontierMath Tier 4 | 80.5% | 39% |
| OTIS Mock AIME 2024-2025 | 100% | 97.2% |
| ProofBench | 100% | 87% |
| LMArena Math | 1510 | 1491 |
| MathArena Final-Answer Competitions | — | 87.8% |
| FrontierMath Erdős | 2.9% | — |

## Knowledge

- Claude Sonnet 5.5: 66.0 (#12)
- Kimi K3: 63.2 (#21)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| GPQA Diamond | 95.6% | 93.1% |
| SimpleQA Verified | 46.5% | 50.6% |
| LMArena Expert | 1540 | 1521 |

## Multimodal

- Claude Sonnet 5.5: 51.5 (#6)
- Kimi K3: 37.8 (#70)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| Furniture Assembly | 75% | 34.2% |
| LMArena Vision | 1289 | — |
| Blueprint-Bench 2 | — | 29.5% |

## Multilingual

- Claude Sonnet 5.5: 55.3 (#30)
- Kimi K3: 56.3 (#21)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| LMArena Non-English | 1452 | 1466 |
| LMArena Chinese | 1522 | 1529 |
| LMArena Russian | 1451 | 1482 |
| LMArena French | — | 1491 |
| LMArena German | — | 1488 |
| LMArena Japanese | — | 1487 |
| LMArena Korean | — | 1458 |
| LMArena Spanish | — | 1472 |

## Instruction Following

- Claude Sonnet 5.5: 78.3 (#11)
- Kimi K3: 77.7 (#14)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| LMArena Instruction Following | 1495 | 1483 |

## Long Context

- Claude Sonnet 5.5: 45.9 (#28)
- Kimi K3: 45.8 (#29)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| LMArena Longer Query | 1498 | 1494 |

## Writing & Preference

- Claude Sonnet 5.5: 66.0 (#40)
- Kimi K3: 76.6 (#4)

| Benchmark | Claude Sonnet 5.5 | Kimi K3 |
|---|---|---|
| LMArena Text | 1471 | 1476 |
| LMArena Creative Writing | 1465 | 1454 |
| LMArena Multi-Turn | 1474 | 1488 |
| EQ-Bench Creative Writing | — | 2082 |
| EQ-Bench 4 | — | 1339 |

## FAQ

### Is Claude Sonnet 5.5 better than Kimi K3?

Claude Sonnet 5.5 is the stronger model overall, scoring 61.9 to 59.5 on the Noometry Index.

### Which is cheaper, Claude Sonnet 5.5 or Kimi K3?

Claude Sonnet 5.5 is cheaper. It lists at $2 per million input tokens and $10 per million output tokens; Kimi K3 lists at $3 and $15.

### Is Claude Sonnet 5.5 or Kimi K3 better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 67.3 versus 61.0 in the Noometry coding category.

### Which has the bigger context window?

Kimi K3 does, with 1.05M tokens against 1M.

### How many benchmarks do Claude Sonnet 5.5 and Kimi K3 share?

29 benchmarks have published results for both models. Claude Sonnet 5.5 has 32 scored results on Noometry and Kimi K3 has 53.