Comparison · prices as of 2026-08-30 · re-verified 2026-10-05
Gemini 2.5 Flash vs Grok 4 Fast
On price alone, Gemini 2.5 Flash (Google) runs about 51% cheaper than Grok 4 Fast for a typical chat workload (2K input + 500 output tokens, 1,000 requests/day). Whether that's the right trade depends on the capability gap — the breakdown below shows where each one wins.
Price per million tokens
| Spec | Gemini 2.5 Flash | Grok 4 Fast |
|---|---|---|
| Input / MTok | $0.30 | $1.25 |
| Output / MTok | $2.50 | $2.50 |
| Context window | 1M | 2M |
| Max output | 66K | 30K |
| Class | workhorse | 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 | Gemini 2.5 Flash | Grok 4 Fast | Cheaper |
|---|---|---|---|
| Light — chatbot 0.5K in / 0.2K out · 200 req/day | $3.90 | $6.75 | Gemini 2.5 Flash |
| Typical — assistant 2K in / 0.5K out · 1K req/day | $55.50 | $113 | Gemini 2.5 Flash |
| Heavy — RAG / agent 8K in / 2K out · 5K req/day | $1,110 | $2,250 | Gemini 2.5 Flash |
Which should you pick?
- Cheapest overall: Gemini 2.5 Flash — about 51% less per month on a typical assistant workload.
- Gemini 2.5 Flash 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 1M — the one to pick if you feed in whole documents or codebases.
- Different classes: Gemini 2.5 Flash is a workhorse model, Grok 4 Fast is a fast / lightweight model — expect Gemini 2.5 Flash to be stronger on hard reasoning and Grok 4 Fast to be faster and cheaper to run.
Frequently asked questions
Is Gemini 2.5 Flash or Grok 4 Fast cheaper?
Gemini 2.5 Flash is cheaper — roughly 51% less per month on a typical assistant workload (2K input + 500 output tokens, 1,000 requests/day).
What do Gemini 2.5 Flash and Grok 4 Fast cost per million tokens?
Gemini 2.5 Flash is $0.30 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, Gemini 2.5 Flash or Grok 4 Fast?
Grok 4 Fast does, at 2M tokens versus 1M for Gemini 2.5 Flash.
When should I choose Grok 4 Fast over Gemini 2.5 Flash?
Choose Grok 4 Fast when you need the extra capability of its fast / lightweight class; drop to Gemini 2.5 Flash when speed and cost matter more than peak quality.
Related comparisons
Sources: Google pricing · xAI pricing. Run your own numbers in the cost calculator.