Model comparison
Claude Sonnet 5.5 vs Grok 4.1 Fast
Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 15× less per token, which makes it the better buy when Claude Sonnet 5.5's lead doesn't matter for your workload.
Last verified . 3 shared benchmarks.
Summary
- They share 3 benchmarks with published results for both. Claude Sonnet 5.5 scores higher in 6 categories and Grok 4.1 Fast in 0 categories; 6 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Sonnet 5.5 leads 88.7 to 30.9.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Sonnet 5.5 and 4% for Grok 4.1 Fast.
- Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $2 / $10 for Claude Sonnet 5.5.
- Claude Sonnet 5.5 accepts more context: 1M tokens versus 128K.
Side by side
| Claude Sonnet 5.5 | Grok 4.1 Fast | |
|---|---|---|
| Provider | Anthropic | xAI |
| Noometry Index | 60.5 | 40.9 |
| Released | 2026-09-28 | 2025-06-27 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 128K |
| Max output | 128K | 30K |
| Input $ / M tokens | $2 | $0.20 |
| Output $ / M tokens | $10 | $0.50 |
| Results tracked | 16 | 32 |
Sponsored placements are available on pages like this one. Advertise on Noometry
Category by category
Coding Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 65.5 (#6), Grok 4.1 Fast: 33.8 (#236)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena WebDev | 1699 | 1241 |
| ALE-Bench | 1,819 | 394.93 |
| FrontierCode | 52.1% | — |
| CursorBench | 55.5% | — |
| FrontierSWE | 61.9% | — |
| SciCode | 61% | — |
| LMArena Coding | — | 1411 |
Agentic & Tool Use Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 44.9 (#14), Grok 4.1 Fast: 36.1 (#35)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| APEX-Agents | 75.5% | — |
| Berkeley Function Calling Leaderboard | — | 69.6% |
| τ²-bench Banking | — | 13.1% |
| LMArena Search | — | 1171 |
| Vending-Bench 2 | — | 1,107 |
Reasoning Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 52.4 (#29), Grok 4.1 Fast: 42.3 (#45)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| SimpleBench | — | 56% |
| NYT Connections (extended) | — | 87.4% |
| CritPt | 31.4% | — |
| LMArena Hard Prompts | — | 1407 |
| Mystery Game Puzzles | 65% | — |
| DTBench | — | 87.7% |
| ForecastBench | — | 61 |
Math Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 88.7 (#4), Grok 4.1 Fast: 30.9 (#201)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| ProofBench | 100% | 4% |
| FrontierMath (Tiers 1-3) | 88.8% | — |
| FrontierMath Tier 4 | 80.5% | — |
| MathArena Final-Answer Competitions | — | 60.9% |
| OTIS Mock AIME 2024-2025 | 100% | — |
| LMArena Math | — | 1408 |
Knowledge Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 66.0 (#11), Grok 4.1 Fast: 32.6 (#203)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| GPQA Diamond | 95.6% | — |
| SimpleQA Verified | 46.5% | — |
| Vectara Hallucination Rate | — | 17.8% |
| LMArena Expert | — | 1398 |
Multimodal Claude Sonnet 5.5 leads
Claude Sonnet 5.5: 53.2 (#5), Grok 4.1 Fast: 36.3 (#71)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Vision | — | 1201 |
| Furniture Assembly | 75% | — |
Multilingual Not comparable
Claude Sonnet 5.5: —, Grok 4.1 Fast: 51.1 (#110)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Non-English | — | 1391 |
| LMArena Chinese | — | 1441 |
| LMArena French | — | 1416 |
| LMArena German | — | 1404 |
| LMArena Japanese | — | 1347 |
| LMArena Korean | — | 1361 |
| LMArena Russian | — | 1387 |
| LMArena Spanish | — | 1411 |
Instruction Following Not comparable
Claude Sonnet 5.5: —, Grok 4.1 Fast: 72.8 (#127)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Instruction Following | — | 1376 |
Long Context Not comparable
Claude Sonnet 5.5: —, Grok 4.1 Fast: 42.4 (#121)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Longer Query | — | 1390 |
Writing & Preference Not comparable
Claude Sonnet 5.5: —, Grok 4.1 Fast: 57.4 (#126)
| Benchmark | Claude Sonnet 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Text | — | 1408 |
| LMArena Creative Writing | — | 1394 |
| EQ-Bench Creative Writing | — | 1327 |
| LMArena Multi-Turn | — | 1389 |
Frequently asked questions
Is Claude Sonnet 5.5 better than Grok 4.1 Fast?
Claude Sonnet 5.5 is the stronger model overall, scoring 60.5 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 15× less per token, which makes it the better buy when Claude Sonnet 5.5's lead doesn't matter for your workload.
Which is cheaper, Claude Sonnet 5.5 or Grok 4.1 Fast?
Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; Claude Sonnet 5.5 lists at $2 and $10.
Is Claude Sonnet 5.5 or Grok 4.1 Fast better for coding?
Claude Sonnet 5.5 scores higher on coding benchmarks: 65.5 versus 33.8 in the Noometry coding category.
Which has the bigger context window?
Claude Sonnet 5.5 does, with 1M tokens against 128K.
How many benchmarks do Claude Sonnet 5.5 and Grok 4.1 Fast share?
3 benchmarks have published results for both models. Claude Sonnet 5.5 has 16 scored results on Noometry and Grok 4.1 Fast has 32.