Comparison · prices as of 2026-07-04 · re-verified 2026-08-18
GPT-5.1 vs Gemini 3 Pro
On price alone, GPT-5.1 (OpenAI) runs about 25% cheaper than Gemini 3 Pro 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 | GPT-5.1 | Gemini 3 Pro |
|---|---|---|
| Input / MTok | $1.25 | $2 |
| Output / MTok | $10 | $12 |
| Context window | 400K | 1M |
| Max output | 128K | 66K |
| Class | frontier | frontier |
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 | GPT-5.1 | Gemini 3 Pro | Cheaper |
|---|---|---|---|
| Light — chatbot 0.5K in / 0.2K out · 200 req/day | $15.75 | $20.40 | GPT-5.1 |
| Typical — assistant 2K in / 0.5K out · 1K req/day | $225 | $300 | GPT-5.1 |
| Heavy — RAG / agent 8K in / 2K out · 5K req/day | $4,500 | $6,000 | GPT-5.1 |
Which should you pick?
- Cheapest overall: GPT-5.1 — about 25% less per month on a typical assistant workload.
- GPT-5.1 is cheaper on both input and output, so it stays cheaper whether your workload is prompt-heavy or generation-heavy.
- Largest context window: Gemini 3 Pro at 1M tokens vs 400K — the one to pick if you feed in whole documents or codebases.
Frequently asked questions
Is GPT-5.1 or Gemini 3 Pro cheaper?
GPT-5.1 is cheaper — roughly 25% less per month on a typical assistant workload (2K input + 500 output tokens, 1,000 requests/day).
What do GPT-5.1 and Gemini 3 Pro cost per million tokens?
GPT-5.1 is $1.25 per million input tokens and $10 per million output. Gemini 3 Pro is $2 input and $12 output. Prices are first-party API list rates as of 2026-07-04.
Which has the larger context window, GPT-5.1 or Gemini 3 Pro?
Gemini 3 Pro does, at 1M tokens versus 400K for GPT-5.1.
When should I choose Gemini 3 Pro over GPT-5.1?
Both are frontier-class models, so choose Gemini 3 Pro when it measurably wins on your own evals or you prefer its provider (Google); otherwise GPT-5.1 does the same job for less.
Related comparisons
Sources: OpenAI pricing · Google pricing. Run your own numbers in the cost calculator.