Gemini 3.1 Pro vs Gemini 3.1 Flash-Lite
Google's Gemini 3.1 Pro and Google's Gemini 3.1 Flash-Lite both target production language workloads, but they price and behave differently. Here is the side-by-side.
Pricing checked against provider documentation on . How we verify
The short answer
Gemini 3.1 Flash-Lite is the cheaper option — roughly 8.0x less on a blended workload, and it suits ultra-cheap high-volume tasks. Gemini 3.1 Pro justifies its premium when you need best price-to-reasoning ratio. Only Gemini 3.1 Pro does native reasoning, which matters for multi-step tasks but adds billable thinking tokens.
Google • Gemini 3.1
$2.00 / $12.00
/ 1M tokens (input / output)
Google's shipping flagship while 3.5 Pro remains unreleased, and the cheapest frontier model by a wide margin. It still tops several hard-reasoning boards including GPQA Diamond and ARC-AGI-2, making it the value choice for research-style workloads — provided you keep prompts under 200K tokens, where the price doubles.
Google • Gemini 3.1
$0.25 / $1.50
/ 1M tokens (input / output)
Google's efficiency tier and a long-term stable target, priced for workloads measured in millions of calls rather than thousands. It gives up the deeper reasoning of 3.5 Flash, so it suits mechanical tasks — classification, extraction, moderation — where a million tokens of context still helps but chain-of-thought does not.
Input price
Gemini 3.1 Flash-Lite is 88% cheaper than Gemini 3.1 Pro on input tokens.
Output price
Gemini 3.1 Flash-Lite is 88% cheaper than Gemini 3.1 Pro on output tokens — usually the side that dominates the bill.
Monthly cost at three workload sizes
Standard (non-batch, non-cached) rates. Reasoning models will exceed these figures because thinking tokens bill as output.
| Workload | Gemini 3.1 Pro | Gemini 3.1 Flash-Lite | Difference |
|---|---|---|---|
| Light — 1M in / 200K out | $4 | $1 | $4 |
| Moderate — 10M in / 2M out | $44 | $6 | $39 |
| Heavy — 100M in / 20M out | $440 | $55 | $385 |
Specification comparison
| Attribute | Gemini 3.1 Pro | Gemini 3.1 Flash-Lite |
|---|---|---|
| Input (/ 1M tokens) | $2.00 | $0.25 |
| Output (/ 1M tokens) | $12.00 | $1.50 |
| Cached input | — | — |
| Context window | 1,048,576 tokens | 1,048,576 tokens |
| Max output | 65,536 tokens | 65,536 tokens |
| Native reasoning | Yes | No |
| Knowledge cutoff | 2025-06 | 2025-01 |
| Relative latency | medium | low |
| Open weights | No | No |
| API model ID | gemini-3.1-pro-preview | gemini-3.1-flash-lite |
| Status | preview | stable |
Gemini 3.1 Pro: Prompts over 200K tokens reprice to $4 input / $18 output per 1M.
Choose Gemini 3.1 Pro if…
- Hard reasoning and research tasks
- Long-context document and video analysis
- Native multimodal pipelines
- Cost-conscious frontier workloads
Choose Gemini 3.1 Flash-Lite if…
- Content moderation at volume
- Classification and routing
- Lightweight summarization
- Cheap long-context retrieval
Frequently asked
Is Gemini 3.1 Pro or Gemini 3.1 Flash-Lite cheaper?
Gemini 3.1 Flash-Lite is cheaper. On a blended 3:1 input-to-output workload it costs about 8.0x less than Gemini 3.1 Pro.
Which has the larger context window, Gemini 3.1 Pro or Gemini 3.1 Flash-Lite?
Both accept up to 1.05M tokens, so context is not a differentiator here.
Should I use Gemini 3.1 Pro or Gemini 3.1 Flash-Lite?
Pick Gemini 3.1 Pro for best price-to-reasoning ratio. Pick Gemini 3.1 Flash-Lite for ultra-cheap high-volume tasks. If cost dominates the decision, Gemini 3.1 Flash-Lite wins; if you need the capability ceiling, benchmark both on your own evals before committing.