Gemini 3.1 Pro Preview vs Gemini 3.5 Flash Lite
For a typical chat reply (2,000 tokens in, 400 out), Gemini 3.1 Pro Preview costs 5.5× as much as Gemini 3.5 Flash Lite: $8.80 against $1.60 per 1,000 requests at list price on 2026-09-28.
| Gemini 3.1 Pro Preview | Gemini 3.5 Flash Lite | |
|---|---|---|
| Input, per 1M tokens | $2.00 | $0.30 |
| Output, per 1M tokens | $12.00 | $2.50 |
| Context window | 1.05M | 1.05M |
| Classification or routing (600 tokens in, 10 out), per 1,000 | $1.32 | $0.205 |
| Chat reply (2,000 in, 400 out), per 1,000 | $8.80 | $1.60 |
| Retrieval-augmented answer (8,000 in, 500 out), per 1,000 | $22.00 | $3.65 |
| Confidence signal | no | no |
| Tool calling | yes | yes |
| BANKING77, correct of 400 | not measured | 305 |
Which one should carry your traffic?
If Gemini 3.5 Flash Lite answers your requests as well as Gemini 3.1 Pro Preview, moving that traffic saves 82% on chat-shaped requests. Averages cannot tell you whether it does for your requests. Gemini 3.5 Flash Lite does not expose a confidence signal through OpenRouter, so Gimbix would test it as a full replacement rather than a first answer.
Gemini 3.1 Pro Preview profile · Gemini 3.5 Flash Lite profile · Measure it on your traffic