Gemini 3.1 Pro vs Gemini 3.5 Flash
Gemini 3.1 Pro and Gemini 3.5 Flash are both current google production-tier models. Gemini 3.5 Flash is meaningfully cheaper at $1.5 / $9 per 1M. Gemini 3.1 Pro leads on reasoning, general knowledge, vision.
Specs side by side
| Metric | Google Gemini 3.1 Pro | Google Gemini 3.5 Flash |
|---|---|---|
| Input price (per 1M) | $2 | $1.5 |
| Output price (per 1M) | $12 | $9 |
| Context window | 2M tokens | 1.0M tokens |
| Speed tier | balanced | fast |
| Open weights | No | No |
| EU region | Yes | Yes |
| Free tier | No | Google AI Studio |
| Prompt caching | Yes | Yes |
| Vision input | Yes | Yes |
| Extended thinking | Yes | Yes |
When to choose each
Choose Gemini 3.1 Pro if…
- You need 2M context (2× more than Gemini 3.5 Flash)
- Reasoning is central to your workload
- General knowledge is central to your workload
Choose Gemini 3.5 Flash if…
- You want a free tier for prototyping
Benchmark delta
Gemini 3.1 Pro leads on
- Reasoning
- General knowledge
- Vision
Gemini 3.5 Flash leads on
Gemini 3.5 Flash has no meaningful benchmark lead in this pair.
FAQ — Gemini 3.1 Pro vs Gemini 3.5 Flash
Gemini 3.1 Pro vs Gemini 3.5 Flash — which is better?
Gemini 3.1 Pro and Gemini 3.5 Flash are both current google production-tier models. Gemini 3.5 Flash is meaningfully cheaper at $1.5 / $9 per 1M. Gemini 3.1 Pro leads on reasoning, general knowledge, vision. The right pick depends on your use case — see "When to choose each" above for a data-driven decision.
How does Gemini 3.1 Pro pricing compare to Gemini 3.5 Flash?
Gemini 3.1 Pro costs $2 / $12 per 1M vs Gemini 3.5 Flash at $1.5 / $9 per 1M. Gemini 3.5 Flash is cheaper on output tokens by roughly 33%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does Gemini 3.1 Pro or Gemini 3.5 Flash have the bigger context window?
Gemini 3.1 Pro has a 2M-token context window — 2× the 1.0M context of Gemini 3.5 Flash. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for Gemini 3.1 Pro or Gemini 3.5 Flash?
Gemini 3.1 Pro: no — Paid-only since 2026-04-01 (previously had free tier via AI Studio). Gemini 3.5 Flash: yes — Reduced daily quota via AI Studio for prototyping.
Which is better for coding — Gemini 3.1 Pro or Gemini 3.5 Flash?
Gemini 3.1 Pro leads on coding benchmarks (Gemini 3.1 Pro: 94/100, Gemini 3.5 Flash: 91/100). For production coding agents also weigh tool-use performance — Gemini 3.1 Pro scores 91, Gemini 3.5 Flash scores 90.