GPT-5.1 Max vs Grok 4 Max: which model should you choose?
We compared GPT-5.1 Max and Grok 4 Max on price, context window and 12 benchmarks. GPT-5.1 Max has the stronger average benchmark score; Grok 4 Max is cheaper on a blended 3:1 basis.
GPT-5.1 Max
GPT-5.1 Max is a frontier model from OpenAI. It offers a 2,000,000-token context window, costs $20.50 per million input tokens and $103.98 per million output tokens, and averages 87.9 across the index's benchmark suite.
- Input
- $20.50 / 1M
- Output
- $103.98 / 1M
- Context
- 2,000,000
- Avg score
- 87.9
- Open weights
- No
Grok 4 Max
Grok 4 Max is a frontier model from xAI. It offers a 2,000,000-token context window, costs $19.70 per million input tokens and $98.29 per million output tokens, and averages 86.6 across the index's benchmark suite.
- Input
- $19.70 / 1M
- Output
- $98.29 / 1M
- Context
- 2,000,000
- Avg score
- 86.6
- Open weights
- No
Specification comparison
| Spec | GPT-5.1 Max | Grok 4 Max | Edge |
|---|---|---|---|
| Input price / 1M | $20.50 | $19.70 | B |
| Output price / 1M | $103.98 | $98.29 | B |
| Context window | 2,000,000 | 2,000,000 | Tie |
| Max output | 8,192 | 16,384 | B |
| Average score | 87.9 | 86.6 | A |
| Arena Elo | 1478.2 | 1491.4 | B |
| Open weights | No | No | Tie |
Benchmark comparison
GPT-5.1 Max wins 6, Grok 4 Max wins 6, and 0 benchmarks are tied. The table shows the modelled score for each model and the gap.
| Benchmark | GPT-5.1 Max | Grok 4 Max | Gap | Winner |
|---|---|---|---|---|
| MMLU-Pro | 91.3 | 87.8 | 3.5 | GPT-5.1 Max |
| GPQA Diamond | 86.4 | 82.0 | 4.4 | GPT-5.1 Max |
| SWE-bench Verified | 75.6 | 74.3 | 1.3 | GPT-5.1 Max |
| HumanEval | 92.2 | 93.4 | 1.2 | Grok 4 Max |
| MATH-500 | 91.3 | 94.6 | 3.3 | Grok 4 Max |
| AIME 2025 | 88.8 | 87.3 | 1.5 | GPT-5.1 Max |
| LiveCodeBench | 80.2 | 81.3 | 1.1 | Grok 4 Max |
| IFEval | 92.2 | 92.5 | 0.3 | Grok 4 Max |
| TruthfulQA | 91.1 | 85.8 | 5.3 | GPT-5.1 Max |
| HellaSwag | 93.1 | 94.1 | 1.0 | Grok 4 Max |
| MMMU | 85.1 | 80.0 | 5.1 | GPT-5.1 Max |
| Arena Elo | 1478.2 | 1491.4 | 13.2 | Grok 4 Max |
Price analysis
On a blended 3:1 input-to-output basis, GPT-5.1 Max costs about $41.37 per million tokens and Grok 4 Max costs about $39.35. Grok 4 Max is roughly 5% cheaper than GPT-5.1 Max. At high volume, that gap compounds quickly, so price should carry real weight unless the quality difference is decisive.
Both models list a 2,000,000-token context window. That is enough for long documents, large codebases and multi-step agent traces.
Verdict
Across 12 shared benchmarks, GPT-5.1 Max wins 6, Grok 4 Max wins 6, and 0 are tied. On the index average, GPT-5.1 Max leads Grok 4 Max by 1.3 points (87.9 versus 86.6).
The price picture favours Grok 4 Max. The context picture is effectively a tie. Those two dimensions often matter more than a few benchmark points once a model is good enough for the task.
If you need a single default, start with GPT-5.1 Max for quality-sensitive work and Grok 4 Max for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.
Choose GPT-5.1 Max if
- You want the higher average benchmark score in this index.
Choose Grok 4 Max if
- Unit cost matters and you want the cheaper blended price.
- You need the larger 16,384-token output limit.
FAQ
Is GPT-5.1 Max better than Grok 4 Max?
On the index average, GPT-5.1 Max leads Grok 4 Max by 1.3 points (87.9 versus 86.6). The better choice depends on price, context and your task. GPT-5.1 Max wins 6 benchmarks, Grok 4 Max wins 6.
Which is cheaper, GPT-5.1 Max or Grok 4 Max?
Grok 4 Max is cheaper on a blended 3:1 basis at about $39.35 per million tokens, versus $41.37 for GPT-5.1 Max.
Which has the larger context window?
Both models list a 2,000,000-token context window.
Are these models open weights?
GPT-5.1 Max is proprietary; Grok 4 Max is proprietary.
Which should I choose for production?
If you need a single default, start with GPT-5.1 Max for quality-sensitive work and Grok 4 Max for high-volume, well-scoped tasks. Run both on a sample of your own traffic before locking in a choice.