Gemini 3.1 Pro vs Gemini 3.5 Flash: API Pricing
Input and output token rates, context windows, and real monthly cost for Gemini 3.1 Pro (Google) and Gemini 3.5 Flash (Google), side by side. Prices are standard on-demand rates as of June 2026.
The short answer
For a typical coding-agent workload (60M in / 12M out per month), Gemini 3.5 Flash is the cheaper option at $198/mo versus $264/mo for Gemini 3.1 Pro - about 25% less. On the headline sticker of 1M input + 1M output, Gemini 3.1 Pro is $14.00 and Gemini 3.5 Flash is $10.50.
Rates at a glance
| Gemini 3.1 Pro | Gemini 3.5 Flash | |
|---|---|---|
| Input ($/1M tokens) | $2.00 | $1.50 |
| Output ($/1M tokens) | $12.00 | $9.00 |
| Blended (1M in + 1M out) | $14.00 | $10.50 |
| Context window | 1,000K | 1,000K |
| Type | Proprietary | Proprietary |
| Provider |
Monthly cost by workload
Estimated monthly API spend at each workload's token volume. Output usually costs several times input, so the winner can flip with your mix.
| Workload | Gemini 3.1 Pro | Gemini 3.5 Flash | Cheaper |
|---|---|---|---|
| Chatbot / assistant 10M in / 3M out | $56.00/mo | $42.00/mo | Gemini 3.5 Flash |
| Coding agent 60M in / 12M out | $264/mo | $198/mo | Gemini 3.5 Flash |
| RAG / summarization 40M in / 4M out | $128/mo | $96.00/mo | Gemini 3.5 Flash |
| Batch / classification 20M in / 2M out | $64.00/mo | $48.00/mo | Gemini 3.5 Flash |
Want your own in/out split? Use the full interactive comparator to rank every model and provider for your exact workload.
Frequently asked questions
Is Gemini 3.1 Pro or Gemini 3.5 Flash cheaper?
It depends on your input/output mix, but for a typical coding-agent workload (60M in / 12M out per month) Gemini 3.5 Flash costs $198/mo versus $264/mo for Gemini 3.1 Pro - about 25% less. On the headline sticker (1M input + 1M output), Gemini 3.1 Pro is $14.00 and Gemini 3.5 Flash is $10.50.
What are the token rates for Gemini 3.1 Pro and Gemini 3.5 Flash?
Gemini 3.1 Pro (Google) is $2.00 per 1M input and $12.00 per 1M output. Gemini 3.5 Flash (Google) is $1.50 per 1M input and $9.00 per 1M output. These are standard on-demand rates, not cached or batch.
Is Gemini 3.1 Pro or Gemini 3.5 Flash open-weight?
Gemini 3.1 Pro is proprietary and Gemini 3.5 Flash is proprietary. Both are closed models billed only through their owner's API.
What context window do Gemini 3.1 Pro and Gemini 3.5 Flash support?
Gemini 3.1 Pro supports 1,000K tokens and Gemini 3.5 Flash supports 1,000K tokens. Some models also step up pricing past a size threshold - check the source pricing pages for long-context tiers.
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