Model comparison
Claude Opus 5.5 vs Grok 4.1 Fast
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 29× less per token, which makes it the better buy when Claude Opus 5.5's lead doesn't matter for your workload.
Last verified . 22 shared benchmarks.
Summary
- They share 22 benchmarks with published results for both. Claude Opus 5.5 scores higher in 10 categories and Grok 4.1 Fast in 0 categories; 10 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Opus 5.5 leads 91.8 to 31.9.
- The biggest single-benchmark swing is ProofBench: 100% for Claude Opus 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 $4 / $20 for Claude Opus 5.5.
- Claude Opus 5.5 accepts more context: 1M tokens versus 128K.
Side by side
| Claude Opus 5.5 | Grok 4.1 Fast | |
|---|---|---|
| Provider | Anthropic | xAI |
| Noometry Index | 68.6 | 41.4 |
| Released | 2026-09-22 | 2025-06-27 |
| Weights | Proprietary | Proprietary |
| Context window | 1M | 128K |
| Max output | 128K | 30K |
| Input $ / M tokens | $4 | $0.20 |
| Output $ / M tokens | $20 | $0.50 |
| Results tracked | 44 | 32 |
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Category by category
Coding Claude Opus 5.5 leads
Claude Opus 5.5: 71.9 (#3), Grok 4.1 Fast: 34.1 (#245)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena WebDev | 1813 | 1242 |
| LMArena Coding | 1547 | 1411 |
| ALE-Bench | 2,147 | 394.93 |
| FrontierCode | 54.6% | — |
| CursorBench | 57.8% | — |
| FrontierSWE | 62.3% | — |
| SciCode | 66.9% | — |
| MirrorCode | 77.4% | — |
Agentic & Tool Use Claude Opus 5.5 leads
Claude Opus 5.5: 45.3 (#15), Grok 4.1 Fast: 36.3 (#39)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| Vending-Bench 2 | 9,235 | 1,107 |
| APEX-Agents | 73.5% | — |
| Berkeley Function Calling Leaderboard | — | 69.6% |
| τ²-bench Banking | — | 13.1% |
| GDP.pdf | 30.6% | — |
| LMArena Search | — | 1171 |
Reasoning Claude Opus 5.5 leads
Claude Opus 5.5: 80.2 (#3), Grok 4.1 Fast: 43.4 (#49)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| NYT Connections (extended) | 88.5% | 87.4% |
| LMArena Hard Prompts | 1535 | 1407 |
| DTBench | 98.9% | 87.7% |
| ARC-AGI-2 | 93.3% | — |
| SimpleBench | — | 56% |
| ARC-AGI-1 | 98.5% | — |
| CritPt | 31.7% | — |
| EBR-Bench | 71.4% | — |
| Mystery Game Puzzles | 71% | — |
| LMCA | 68.2% | — |
| Epoch Capabilities Index | 167.33 | — |
| ForecastBench | — | 61 |
Math Claude Opus 5.5 leads
Claude Opus 5.5: 91.8 (#3), Grok 4.1 Fast: 31.9 (#221)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| ProofBench | 100% | 4% |
| LMArena Math | 1506 | 1408 |
| FrontierMath (Tiers 1-3) | 91.2% | — |
| FrontierMath Tier 4 | 95% | — |
| MathArena Final-Answer Competitions | — | 60.9% |
| OTIS Mock AIME 2024-2025 | 100% | — |
| FrontierMath Erdős | 2.9% | — |
Knowledge Claude Opus 5.5 leads
Claude Opus 5.5: 66.4 (#10), Grok 4.1 Fast: 33.1 (#207)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Expert | 1547 | 1399 |
| GPQA Diamond | 90.6% | — |
| SimpleQA Verified | 72.2% | — |
| Vectara Hallucination Rate | — | 17.8% |
Multimodal Claude Opus 5.5 leads
Claude Opus 5.5: 57.8 (#1), Grok 4.1 Fast: 37.0 (#76)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Vision | 1321 | 1201 |
| Blueprint-Bench 2 | 51.2% | — |
| Furniture Assembly | 83.3% | — |
Multilingual Claude Opus 5.5 leads
Claude Opus 5.5: 59.1 (#2), Grok 4.1 Fast: 51.0 (#114)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Non-English | 1507 | 1391 |
| LMArena Chinese | 1588 | 1441 |
| LMArena French | 1514 | 1415 |
| LMArena Russian | 1520 | 1387 |
| LMArena Spanish | 1507 | 1413 |
| LMArena German | — | 1404 |
| LMArena Japanese | — | 1349 |
| LMArena Korean | — | 1361 |
Instruction Following Claude Opus 5.5 leads
Claude Opus 5.5: 80.0 (#3), Grok 4.1 Fast: 72.7 (#133)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Instruction Following | 1537 | 1376 |
Long Context Claude Opus 5.5 leads
Claude Opus 5.5: 47.1 (#19), Grok 4.1 Fast: 42.4 (#126)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Longer Query | 1532 | 1390 |
Writing & Preference Claude Opus 5.5 leads
Claude Opus 5.5: 78.2 (#3), Grok 4.1 Fast: 57.2 (#131)
| Benchmark | Claude Opus 5.5 | Grok 4.1 Fast |
|---|---|---|
| LMArena Text | 1515 | 1408 |
| LMArena Creative Writing | 1533 | 1394 |
| EQ-Bench Creative Writing | 2050 | 1327 |
| LMArena Multi-Turn | 1499 | 1389 |
Frequently asked questions
Is Claude Opus 5.5 better than Grok 4.1 Fast?
Claude Opus 5.5 is the stronger model overall, scoring 68.6 to 41.4 on the Noometry Index. Grok 4.1 Fast costs 29× 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 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 Opus 5.5 lists at $4 and $20.
Is Claude Opus 5.5 or Grok 4.1 Fast better for coding?
Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 34.1 in the Noometry coding category.
Which has the bigger context window?
Claude Opus 5.5 does, with 1M tokens against 128K.
How many benchmarks do Claude Opus 5.5 and Grok 4.1 Fast share?
22 benchmarks have published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and Grok 4.1 Fast has 32.