GPT-5.5 vs Grok 4.1 Fast
A direct API-pricing comparison between GPT-5.5 and Grok 4.1 Fast. Below: every cost dimension side by side, then the bottom line for a typical workload.
Bottom line
For a typical 5K-in / 1K-out request, Grok 4.1 Fast is the cheaper choice at $0.0015 per call — 36.7× less than GPT-5.5 at $0.055.
| GPT-5.5OpenAI | Grok 4.1 FastxAI | |
|---|---|---|
| Input / 1M tokens | $5.00 | $0.200 |
| Output / 1M tokens | $30.00 | $0.500 |
| Cached input / 1M | — | — |
| Context window | 400K | 256K |
| Provider | OpenAI | xAI |
Green = cheaper on that line. Prices are estimates from public pricing pages; verify against OpenAI and xAI before relying on them.
Which is cheaper, GPT-5.5 or Grok 4.1 Fast?
On output tokens — usually the dominant cost — GPT-5.5 charges $30.00 per million versus $0.500 for Grok 4.1 Fast. The right pick depends on your input/output ratio and how much you can serve from cache. Use the calculator to model your exact traffic.