The role it plays
The gemini 3.1 flash lite model is the entry point into Google's Gemini 3 line — the cheapest model in this comparison, and the one built for workloads where cost per call matters more than squeezing out every last point of reasoning depth: content moderation, lightweight classification, chat widgets fielding thousands of short conversations, and background agents that fire off frequent tool calls.
The million-token window in practice
A 1,048,576-token context window is large enough to hold a full customer support history, a mid-size codebase, or a stack of PDFs without truncation — even on the cheapest model in the lineup. Output tops out at 65,536 tokens per response, which covers structured data extraction, summaries, and multi-turn tool plans comfortably.
What you pay
Gemini 3.1 Flash Lite costs $0.25 per million input tokens and $1.50 per million output tokens — the lowest rate of any model in this comparison. Cached input drops further, to $0.025 per million tokens, a real saving for apps that reuse a large system prompt or reference document across many requests. Its knowledge cutoff is listed as January 2025, so anything that happened after that needs to come in through retrieval or tool use rather than the model's training data.
Rough cost picture:
- Input: $0.25 per million tokens
- Output: $1.50 per million tokens
- Cached input: $0.025 per million tokens
- Context window: 1,048,576 tokens
- Max output: 65,536 tokens
Positioning inside Google's Gemini 3 family
Compared to Gemini 3.5 Flash Lite ($0.30 input / $2.50 output), 3.1 Flash Lite is the older, cheaper generation — a reasonable default if your task doesn't need whatever incremental improvements came with the 3.5 line, and a good starting point before paying more for Gemini 3.6 Flash ($1.50 / $7.50) or Gemini 3.5 Flash ($1.50 / $9.00). It still supports function calling, reasoning, and vision, so the lower price isn't a case of stripped-out features — it's the same feature set at a smaller footprint.
One thing to watch
Its capability score (89.0) sits just under the two newer models in this lineup (both 89.4), a small but real gap. For latency- and cost-sensitive workloads that lean on high call volume, that gap is usually worth trading for the lower price — but for anything where output quality directly affects the product, it's worth running your own comparison rather than assuming the newer, pricier sibling automatically wins.