# Claude Sonnet 5.5 vs Grok 4 Fast

> Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 39.0 on the Noometry Index.

- Canonical page: https://noometry.com/compare/claude-sonnet-5-5-vs-grok-4-fast
- Last updated: 2026-10-10
- Shared benchmarks: 1

## Summary

- They share 1 benchmark with published results for both. Claude Sonnet 5.5 scores higher in 5 categories and Grok 4 Fast in 0 categories; 5 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5.5 leads 88.7 to 36.1.

## Snapshot

| | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| Provider | Anthropic | xAI |
| Noometry Index | 60.5 | 39.0 |
| Rank | 10 | 164 |
| Context | 1M | — |
| Input $/M | $2 | — |
| Output $/M | $10 | — |
| Weights | Proprietary | Proprietary |

## Coding

- Claude Sonnet 5.5: 65.5 (#6)
- Grok 4 Fast: 32.3 (#264)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| LMArena WebDev | 1699 | 1160 |
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| WeirdML | — | 42.9% |
| LMArena Coding | — | 1429 |
| ALE-Bench | 1,819 | — |

## Agentic & Tool Use

- Claude Sonnet 5.5: 44.9 (#14)
- Grok 4 Fast: 29.3 (#80)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| APEX-Agents | 75.5% | — |
| τ²-bench Banking | — | 15.7% |
| Cybench | — | 30% |
| LMArena Search | — | 1171 |

## Reasoning

- Claude Sonnet 5.5: 52.4 (#29)
- Grok 4 Fast: 22.5 (#179)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| ARC-AGI-2 | — | 5.3% |
| Kagi LLM Benchmark | — | 66.1% |
| ARC-AGI-1 | — | 48.5% |
| CritPt | 31.4% | — |
| LMArena Hard Prompts | — | 1413 |
| Mystery Game Puzzles | 65% | — |
| DTBench | — | 82.7% |
| Epoch Capabilities Index | — | 144.21 |
| ForecastBench | — | 60.5 |

## Math

- Claude Sonnet 5.5: 88.7 (#4)
- Grok 4 Fast: 36.1 (#126)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| OTIS Mock AIME 2024-2025 | 100% | — |
| ProofBench | 100% | — |
| LMArena Math | — | 1419 |

## Knowledge

- Claude Sonnet 5.5: 66.0 (#11)
- Grok 4 Fast: 31.5 (#211)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
| Vectara Hallucination Rate | — | 19.7% |
| LMArena Expert | — | 1411 |

## Multimodal

- Claude Sonnet 5.5: 53.2 (#5)
- Grok 4 Fast: —

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| Furniture Assembly | 75% | — |

## Multilingual

- Claude Sonnet 5.5: —
- Grok 4 Fast: 51.5 (#106)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| LMArena Non-English | — | 1397 |
| LMArena Chinese | — | 1458 |
| LMArena French | — | 1433 |
| LMArena German | — | 1383 |
| LMArena Japanese | — | 1358 |
| LMArena Korean | — | 1359 |
| LMArena Russian | — | 1387 |
| LMArena Spanish | — | 1414 |

## Instruction Following

- Claude Sonnet 5.5: —
- Grok 4 Fast: 73.4 (#116)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| LMArena Instruction Following | — | 1388 |

## Long Context

- Claude Sonnet 5.5: —
- Grok 4 Fast: 63.2 (#3)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| Fiction.LiveBench | — | 94.4% |
| LMArena Longer Query | — | 1415 |

## Writing & Preference

- Claude Sonnet 5.5: —
- Grok 4 Fast: 60.2 (#96)

| Benchmark | Claude Sonnet 5.5 | Grok 4 Fast |
|---|---|---|
| LMArena Text | — | 1407 |
| LMArena Creative Writing | — | 1388 |
| LMArena Multi-Turn | — | 1414 |

## FAQ

### Is Claude Sonnet 5.5 better than Grok 4 Fast?

Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 39.0 on the Noometry Index.

### Is Claude Sonnet 5.5 or Grok 4 Fast better for coding?

Claude Sonnet 5.5 scores higher on coding benchmarks: 65.5 versus 32.3 in the Noometry coding category.

### How many benchmarks do Claude Sonnet 5.5 and Grok 4 Fast share?

1 benchmark has published results for both models. Claude Sonnet 5.5 has 16 scored results on Noometry and Grok 4 Fast has 30.