Model comparison
GPT-5 Nano vs Grok 4.1 Fast
Grok 4.1 Fast is the stronger model overall, scoring 40.9 to 33.4 on the Noometry Index. GPT-5 Nano costs 2.0× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.
Last verified . 23 shared benchmarks.
Summary
- They share 23 benchmarks with published results for both. GPT-5 Nano scores higher in 2 categories and Grok 4.1 Fast in 8 categories; 9 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Grok 4.1 Fast leads 42.3 to 16.4.
- The biggest single-benchmark swing is DTBench: 62.7% for GPT-5 Nano and 87.7% for Grok 4.1 Fast.
- GPT-5 Nano is cheaper at $0.05 / $0.40 per million input/output tokens, against $0.20 / $0.50 for Grok 4.1 Fast.
- GPT-5 Nano accepts more context: 400K tokens versus 128K.
Side by side
| GPT-5 Nano | Grok 4.1 Fast | |
|---|---|---|
| Provider | OpenAI | xAI |
| Noometry Index | 33.4 | 40.9 |
| Released | 2025-08-07 | 2025-06-27 |
| Weights | Proprietary | Proprietary |
| Context window | 400K | 128K |
| Max output | 128K | 30K |
| Input $ / M tokens | $0.05 | $0.20 |
| Output $ / M tokens | $0.40 | $0.50 |
| Results tracked | 48 | 32 |
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Category by category
Coding Too close to call
GPT-5 Nano: 33.3 (#248), Grok 4.1 Fast: 33.8 (#236)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Coding | 1351 | 1411 |
| ALE-Bench | 718.67 | 394.93 |
| SWE-bench Verified (bash only) | 34.8% | — |
| LMArena WebDev | — | 1241 |
| WeirdML | 38.1% | — |
Agentic & Tool Use Grok 4.1 Fast leads
GPT-5 Nano: 25.6 (#99), Grok 4.1 Fast: 36.1 (#35)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| Berkeley Function Calling Leaderboard | 51.5% | 69.6% |
| Terminal-Bench | 21.8% | — |
| τ²-bench Banking | — | 13.1% |
| LMArena Search | — | 1171 |
| Vending-Bench 2 | — | 1,107 |
Reasoning Grok 4.1 Fast leads
GPT-5 Nano: 16.4 (#291), Grok 4.1 Fast: 42.3 (#45)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Hard Prompts | 1329 | 1407 |
| DTBench | 62.7% | 87.7% |
| ForecastBench | 59.1 | 61 |
| ARC-AGI-2 | 2.6% | — |
| SimpleBench | — | 56% |
| Kagi LLM Benchmark | 62.2% | — |
| NYT Connections (extended) | — | 87.4% |
| ARC-AGI-1 | 20.7% | — |
| Chess Puzzles | 27% | — |
| Mystery Game Puzzles | 9% | — |
| LMCA | 7.9% | — |
| Epoch Capabilities Index | 139.39 | — |
Math Grok 4.1 Fast leads
GPT-5 Nano: 29.1 (#221), Grok 4.1 Fast: 30.9 (#201)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| ProofBench | 12% | 4% |
| LMArena Math | 1318 | 1408 |
| FrontierMath (Tiers 1-3) | 20% | — |
| FrontierMath Tier 4 | 2.4% | — |
| MathArena Final-Answer Competitions | — | 60.9% |
| OTIS Mock AIME 2024-2025 | 81.1% | — |
| Omni-MATH | 54.6% | — |
| MATH Level 5 | 95.2% | — |
| FrontierMath (Feb 2025 set) | 8.3% | — |
| FrontierMath Tier 4 (v1) | 2.1% | — |
Knowledge GPT-5 Nano leads
GPT-5 Nano: 35.8 (#166), Grok 4.1 Fast: 32.6 (#203)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| Vectara Hallucination Rate | 10.5% | 17.8% |
| LMArena Expert | 1321 | 1398 |
| GPQA Diamond | 69.4% | — |
| SimpleQA Verified | 11.7% | — |
| MMLU-Pro | 77.8% | — |
| GPQA (HELM) | 67.9% | — |
Multimodal Grok 4.1 Fast leads
GPT-5 Nano: 30.7 (#102), Grok 4.1 Fast: 36.3 (#71)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Vision | 1159 | 1201 |
| VPCT | 37.2% | — |
Multilingual Grok 4.1 Fast leads
GPT-5 Nano: 45.5 (#167), Grok 4.1 Fast: 51.1 (#110)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Non-English | 1313 | 1391 |
| LMArena Chinese | 1355 | 1441 |
| LMArena German | 1329 | 1404 |
| LMArena Korean | 1269 | 1361 |
| LMArena Russian | 1296 | 1387 |
| LMArena Spanish | 1360 | 1411 |
| LMArena French | — | 1416 |
| LMArena Japanese | — | 1347 |
Instruction Following GPT-5 Nano leads
GPT-5 Nano: 75.2 (#72), Grok 4.1 Fast: 72.8 (#127)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Instruction Following | 1306 | 1376 |
| IFEval | 93.2% | — |
Long Context Grok 4.1 Fast leads
GPT-5 Nano: 31.3 (#275), Grok 4.1 Fast: 42.4 (#121)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Longer Query | 1313 | 1390 |
| Fiction.LiveBench | 44.4% | — |
Writing & Preference Grok 4.1 Fast leads
GPT-5 Nano: 39.4 (#244), Grok 4.1 Fast: 57.4 (#126)
| Benchmark | GPT-5 Nano | Grok 4.1 Fast |
|---|---|---|
| LMArena Text | 1320 | 1408 |
| LMArena Creative Writing | 1250 | 1394 |
| EQ-Bench Creative Writing | 705 | 1327 |
| LMArena Multi-Turn | 1311 | 1389 |
| WildBench | 80.6% | — |
Frequently asked questions
Is GPT-5 Nano better than Grok 4.1 Fast?
Grok 4.1 Fast is the stronger model overall, scoring 40.9 to 33.4 on the Noometry Index. GPT-5 Nano costs 2.0× less per token, which makes it the better buy when Grok 4.1 Fast's lead doesn't matter for your workload.
Which is cheaper, GPT-5 Nano or Grok 4.1 Fast?
GPT-5 Nano is cheaper. It lists at $0.05 per million input tokens and $0.40 per million output tokens; Grok 4.1 Fast lists at $0.20 and $0.50.
Is GPT-5 Nano or Grok 4.1 Fast better for coding?
They score almost the same on coding (33.3 vs 33.8); test both on your own repository before choosing.
Which has the bigger context window?
GPT-5 Nano does, with 400K tokens against 128K.
How many benchmarks do GPT-5 Nano and Grok 4.1 Fast share?
23 benchmarks have published results for both models. GPT-5 Nano has 48 scored results on Noometry and Grok 4.1 Fast has 32.