Home / Compare / Gemini 3.1 Pro Preview vs Gemini 3.8 Flash

Gemini 3.1 Pro Preview vs Gemini 3.8 Flash

For a typical chat reply (2,000 tokens in, 400 out), Gemini 3.1 Pro Preview costs 2.9× as much as Gemini 3.8 Flash: $8.80 against $3.00 per 1,000 requests at list price on 2026-09-28.

Gemini 3.1 Pro PreviewGemini 3.8 Flash
Input, per 1M tokens$2.00$0.75
Output, per 1M tokens$12.00$3.75
Context window1.05M1.05M
Classification or routing (600 tokens in, 10 out), per 1,000$1.32$0.487
Chat reply (2,000 in, 400 out), per 1,000$8.80$3.00
Retrieval-augmented answer (8,000 in, 500 out), per 1,000$22.00$7.88
Confidence signalnono
Tool callingyesyes
BANKING77, correct of 400not measured331

Which one should carry your traffic?

If Gemini 3.8 Flash answers your requests as well as Gemini 3.1 Pro Preview, moving that traffic saves 66% on chat-shaped requests. Averages cannot tell you whether it does for your requests. Gemini 3.8 Flash 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 3.8 Flash profile · Measure it on your traffic