Model comparison
Grok 4.1 Fast vs Step 5 Preview
Step 5 Preview is the stronger model overall, scoring 43.8 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 5.2× less per token, which makes it the better buy when Step 5 Preview's lead doesn't matter for your workload.
Last verified . 1 shared benchmarks.
StepFunSummary
- They share 1 benchmark with published results for both. Grok 4.1 Fast scores higher in 1 category and Step 5 Preview in 1 category; 2 gaps are clear of the uncertainty.
- The widest gap is in coding, where Step 5 Preview leads 50.6 to 33.8.
- Grok 4.1 Fast is cheaper at $0.20 / $0.50 per million input/output tokens, against $1 / $2.70 for Step 5 Preview.
- Step 5 Preview accepts more context: 1.02M tokens versus 128K.
Side by side
| Grok 4.1 Fast | Step 5 Preview | |
|---|---|---|
| Provider | xAI | StepFun |
| Noometry Index | 40.9 | 43.8 |
| Released | 2025-06-27 | 2026-09-16 |
| Weights | Proprietary | Proprietary |
| Context window | 128K | 1.02M |
| Max output | 30K | 66K |
| Input $ / M tokens | $0.20 | $1 |
| Output $ / M tokens | $0.50 | $2.70 |
| Results tracked | 32 | 3 |
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Category by category
Coding Step 5 Preview leads
Grok 4.1 Fast: 33.8 (#236), Step 5 Preview: 50.6 (#40)
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| LMArena WebDev | 1241 | 1569 |
| SciCode | — | 58.9% |
| LMArena Coding | 1411 | — |
| ALE-Bench | 394.93 | — |
Agentic & Tool Use Not comparable
Grok 4.1 Fast: 36.1 (#35), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| Berkeley Function Calling Leaderboard | 69.6% | — |
| τ²-bench Banking | 13.1% | — |
| LMArena Search | 1171 | — |
| Vending-Bench 2 | 1,107 | — |
Reasoning Grok 4.1 Fast leads
Grok 4.1 Fast: 42.3 (#45), Step 5 Preview: 38.0 (#58)
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| SimpleBench | 56% | — |
| NYT Connections (extended) | 87.4% | — |
| CritPt | — | 20.9% |
| LMArena Hard Prompts | 1407 | — |
| DTBench | 87.7% | — |
| ForecastBench | 61 | — |
Math Not comparable
Grok 4.1 Fast: 30.9 (#201), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| MathArena Final-Answer Competitions | 60.9% | — |
| ProofBench | 4% | — |
| LMArena Math | 1408 | — |
Knowledge Not comparable
Grok 4.1 Fast: 32.6 (#203), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| Vectara Hallucination Rate | 17.8% | — |
| LMArena Expert | 1398 | — |
Multimodal Not comparable
Grok 4.1 Fast: 36.3 (#71), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| LMArena Vision | 1201 | — |
Multilingual Not comparable
Grok 4.1 Fast: 51.1 (#110), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| 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
Grok 4.1 Fast: 72.8 (#127), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| LMArena Instruction Following | 1376 | — |
Long Context Not comparable
Grok 4.1 Fast: 42.4 (#121), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| LMArena Longer Query | 1390 | — |
Writing & Preference Not comparable
Grok 4.1 Fast: 57.4 (#126), Step 5 Preview: —
| Benchmark | Grok 4.1 Fast | Step 5 Preview |
|---|---|---|
| LMArena Text | 1408 | — |
| LMArena Creative Writing | 1394 | — |
| EQ-Bench Creative Writing | 1327 | — |
| LMArena Multi-Turn | 1389 | — |
Frequently asked questions
Is Grok 4.1 Fast better than Step 5 Preview?
Step 5 Preview is the stronger model overall, scoring 43.8 to 40.9 on the Noometry Index. Grok 4.1 Fast costs 5.2× less per token, which makes it the better buy when Step 5 Preview's lead doesn't matter for your workload.
Which is cheaper, Grok 4.1 Fast or Step 5 Preview?
Grok 4.1 Fast is cheaper. It lists at $0.20 per million input tokens and $0.50 per million output tokens; Step 5 Preview lists at $1 and $2.70.
Is Grok 4.1 Fast or Step 5 Preview better for coding?
Step 5 Preview scores higher on coding benchmarks: 50.6 versus 33.8 in the Noometry coding category.
Which has the bigger context window?
Step 5 Preview does, with 1.02M tokens against 128K.
How many benchmarks do Grok 4.1 Fast and Step 5 Preview share?
1 benchmark has published results for both models. Grok 4.1 Fast has 32 scored results on Noometry and Step 5 Preview has 3.