Prices → Compare → Gemini 3.1 Pro vs Gemini 2.5 Flash-Lite
Gemini 3.1 Pro vs Gemini 2.5 Flash-Lite: API cost compared
Gemini 3.1 Pro lists at $2.000 in / $12.00 out per 1M tokens. Gemini 2.5 Flash-Lite lists at $0.100 in / $0.400. Sticker price only tells you so much — below is what each actually costs across eight production workloads.
Side by side
| Gemini 3.1 Pro | Gemini 2.5 Flash-Lite | |
|---|---|---|
| Provider | ||
| Input per 1M | $2.000 | $0.100 |
| Output per 1M | $12.00 | $0.400 |
| Cached input per 1M | not published | not published |
| Context window | 1M | 1M |
| Blended per 1M (3:1) | $4.500 | $0.175 |
Monthly cost by workload
Caching applied at each workload's typical hit rate. This is where the two models actually separate.
| Workload | Gemini 3.1 Pro | Gemini 2.5 Flash-Lite | Cheaper | Difference |
|---|---|---|---|---|
| Customer support chatbot | $390.00 | $16.00 | Gemini 2.5 Flash-Lite | $374.00 (96%) |
| RAG document Q&A | $464.00 | $20.80 | Gemini 2.5 Flash-Lite | $443.20 (96%) |
| Coding agent | $344.00 | $14.80 | Gemini 2.5 Flash-Lite | $329.20 (96%) |
| Bulk summarization | $2,880 | $136.00 | Gemini 2.5 Flash-Lite | $2,744 (95%) |
| Structured data extraction | $5,000 | $225.00 | Gemini 2.5 Flash-Lite | $4,775 (96%) |
| Long-form content generation | $520.00 | $18.00 | Gemini 2.5 Flash-Lite | $502.00 (97%) |
| Email triage agent | $1,360 | $62.00 | Gemini 2.5 Flash-Lite | $1,298 (95%) |
| Translation pipeline | $3,330 | $118.50 | Gemini 2.5 Flash-Lite | $3,212 (96%) |
How to read this
Gemini 2.5 Flash-Lite is cheaper on the majority of these workloads, but "majority" is not the decision. The output:input price ratio is 6.0 for Gemini 3.1 Pro and 4.0 for Gemini 2.5 Flash-Lite. If your traffic is output-heavy — long-form drafting, translation — the model with the lower output price wins regardless of what the input price suggests. If you are input-heavy — RAG, bulk summarization, agents re-reading a codebase — the cached input rate matters more than either headline number.
Cost is also not the only axis. This site does not benchmark quality, latency, or rate limits, and a model that is 3x cheaper but needs two attempts per task is not cheaper. Use these numbers to size a bill, then validate on your own evals.
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| Model | In /1M | Out /1M | Monthly | vs best |
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