Comparison · prices as of 2026-08-30 · re-verified 2026-10-05
Grok 4 vs Grok 4 Fast
Grok 4 (xAI) and Grok 4 Fast (xAI) price within 0% of each other on a typical chat workload (2K input + 500 output tokens, 1,000 requests/day) — close enough that capability and latency should decide it, not the bill.
Price per million tokens
| Spec | Grok 4 | Grok 4 Fast |
|---|---|---|
| Input / MTok | $1.25 | $1.25 |
| Output / MTok | $2.50 | $2.50 |
| Context window | 256K | 2M |
| Max output | 64K | 30K |
| Class | frontier | fast / lightweight |
Estimated monthly cost by workload
Same models, three realistic usage levels. The gap between them scales with volume, so the right pick can change as you grow.
| Workload | Grok 4 | Grok 4 Fast | Cheaper |
|---|---|---|---|
| Light — chatbot 0.5K in / 0.2K out · 200 req/day | $6.75 | $6.75 | Grok 4 |
| Typical — assistant 2K in / 0.5K out · 1K req/day | $113 | $113 | Grok 4 |
| Heavy — RAG / agent 8K in / 2K out · 5K req/day | $2,250 | $2,250 | Grok 4 |
Which should you pick?
- Price is close to a wash (0% apart on a typical workload), so decide on capability and latency, not cost.
- Grok 4 is cheaper on both input and output, so it stays cheaper whether your workload is prompt-heavy or generation-heavy.
- Largest context window: Grok 4 Fast at 2M tokens vs 256K — the one to pick if you feed in whole documents or codebases.
- Different classes: Grok 4 is a frontier model, Grok 4 Fast is a fast / lightweight model — expect Grok 4 to be stronger on hard reasoning and Grok 4 Fast to be faster and cheaper to run.
Frequently asked questions
Is Grok 4 or Grok 4 Fast cheaper?
They are close: on a typical assistant workload the difference is only about 0%, with Grok 4 marginally cheaper.
What do Grok 4 and Grok 4 Fast cost per million tokens?
Grok 4 is $1.25 per million input tokens and $2.50 per million output. Grok 4 Fast is $1.25 input and $2.50 output. Prices are first-party API list rates as of 2026-08-30.
Which has the larger context window, Grok 4 or Grok 4 Fast?
Grok 4 Fast does, at 2M tokens versus 256K for Grok 4.
When should I choose Grok 4 Fast over Grok 4?
Choose Grok 4 Fast when you need the extra capability of its fast / lightweight class; drop to Grok 4 when speed and cost matter more than peak quality.
Related comparisons
Sources: xAI pricing · xAI pricing. Run your own numbers in the cost calculator.