Gemini 3.1 Pro vs Gemini 3.5 Flash — Google’s Pro tier versus its fast, cheap Flash tier. Below is the full side-by-side: specifications, API pricing, context window, local hardware requirements, and a clear, data-driven recommendation on which to pick.
| Spec | Gemini 3.1 Pro | Gemini 3.5 Flash |
|---|---|---|
| Developer | ||
| Type | LLM (multimodal) | LLM (multimodal) |
| Parameters | Undisclosed | Undisclosed |
| Context window | 1.05M | 1M |
| Modality | Text, Image, Audio, Video → Text | Text, Image, Audio, Video → Text |
| License | Proprietary | Proprietary |
| Open weights | ❌ No | ❌ No |
| Input price ($/1M) | $2.00 | $1.50 |
| Output price ($/1M) | $12.00 | $9.00 |
| VRAM (4-bit) | — | — |
| Min GPU (local) | — | — |
| Released | 2026 | 2026 |
Key differences
- Cost: Gemini 3.5 Flash is 33% cheaper than Gemini 3.1 Pro on a blended-token basis.
- Context: Gemini 3.1 Pro wins on context window (1.05M vs 1M) — better for long documents, large codebases and big RAG inputs.
- Openness: both are proprietary, API-only models — no self-hosting option for either.
Which should you choose?
Choose Gemini 3.1 Pro if you need the larger context window.
Choose Gemini 3.5 Flash if you want the lower per-token cost for high-volume workloads.
→ Estimate real costs in the API cost calculator · check local hardware in the VRAM calculator · browse all 30+ models.
All specs and prices are pulled live from our AI models database and kept current. Compare either model against others, or estimate your own monthly spend with the free calculators above.