GPT-5.1 vs Grok 4 Fast
OpenAI vs xAI — benchmarks, pricing, and capabilities side by side.
- •GPT-5.1 has the higher intelligence index (89 vs 78.7)
- •Grok 4 Fast is cheaper ($0.20 vs $1.25 per 1M input)
- •GPT-5.1 is faster
- •Grok 4 Fast has a larger context window (2M)
| GPT-5.1 | Grok 4 Fast | |
|---|---|---|
| Intelligence index | 89 | 78.7 |
| Developer | OpenAI | xAI |
| Type | LLM | LLM |
| Access | API only | API only |
| Context window | 400,000 tokens | 2,000,000 tokens |
| Input price | $1.25 / 1M | $0.20 / 1M |
| Output price | $10.00 / 1M | $0.50 / 1M |
| Speed | 115 tok/s | 90 tok/s |
| Released | November 12, 2025 | September 19, 2025 |
| Parameters | — | — |
| Input modalities | Text, Image | Text, Image |
| Output modalities | Text | Text |
Shared benchmarks
GPT-5.1
Grok 4 Fast
AIME 2025
94
92
GPQA Diamond
88.1
85.7
Humanity’s Last Exam
26.5
20
LiveCodeBench
86.8
80
MMLU-Pro
87
85