Which is cheaper, Gemini 2.5 Flash or Gemini 3.1 Pro?

Gemini 2.5 Flash. On a task of 1,500 input and 500 output tokens across 3 calls, Gemini 2.5 Flash costs $0.00510 per task against $0.02700 for Gemini 3.1 Pro, which makes it 5.29x cheaper (a 81% saving).

How much do Gemini 2.5 Flash and Gemini 3.1 Pro charge per million tokens?

Gemini 2.5 Flash: $0.3 per million input tokens and $2.5 per million output tokens. Gemini 3.1 Pro: $2 input and $12 output. These are published list rates as of August 2026, excluding cached, batch and long-context tiers.

What does a million tasks cost on Gemini 2.5 Flash vs Gemini 3.1 Pro?

At the same fixed profile, one million tasks cost $5,100 on Gemini 2.5 Flash and $27,000 on Gemini 3.1 Pro. The gap comes entirely from list-price differences, not from any difference in the work done.

Model price comparisons · August 2026

Gemini 2.5 Flash vs Gemini 3.1 Pro: API pricing compared

Same task, same tokens, two invoices. Every figure on this page is computed from our open pricing dataset, not copied from a blog post.

Gemini 2.5 Flash is 5.29x cheaper than Gemini 3.1 Pro on a realistic task profile of 1,500 input and 500 output tokens per call, 3 calls per task: $0.00510 against $0.02700 per task, a 81% saving on identical work. Run a million tasks a month and that is the difference between $5,100 and $27,000.

Model	Input $/1M tok	Output $/1M tok	Output multiple	$/task	$/1M tasks
Gemini 2.5 FlashGoogle · fast	$0.3	$2.5	8.33x	$0.00510	$5,100
Gemini 3.1 ProGoogle · frontier	$2	$12	6x	$0.02700	$27,000

Monthly bill at three volumes

Tasks / month	Gemini 2.5 Flash	Gemini 3.1 Pro	Gap
10,000	$51	$270	$219
100,000	$510	$2,700	$2,190
1,000,000	$5,100	$27,000	$21,900

Where the money goes on each

Gemini 2.5 Flash prices output at 8.33x its input rate, so on this profile output is 74% of its task cost. Gemini 3.1 Pro prices output at 6x input, putting output at 67% of cost. The model with the higher output multiple rewards capping response length more; the one with the higher input share rewards prompt caching and context trimming more. Cost tells you nothing about quality: run both on twenty of your real cases before deciding, and treat the cheaper model as the default until it demonstrably fails.

Break-even against a dedicated GPU

Against a $2/hour dedicated instance ($1,460/month fixed), self-hosting overtakes Gemini 2.5 Flash at 286,275 tasks per month and overtakes Gemini 3.1 Pro at 54,074 tasks per month. The full method is in the self-hosting break-even guide.

Pricing the self-hosted side? Compare on-demand GPU rates:

Compare GPU cloud pricing →

Plug your own token counts into the $/task calculator, or read the full ten-model pricing comparison.

Compare against other models

Frequently asked

Which is cheaper, Gemini 2.5 Flash or Gemini 3.1 Pro?: Gemini 2.5 Flash. On a task of 1,500 input and 500 output tokens across 3 calls, Gemini 2.5 Flash costs $0.00510 per task against $0.02700 for Gemini 3.1 Pro, which makes it 5.29x cheaper (a 81% saving).
How much do Gemini 2.5 Flash and Gemini 3.1 Pro charge per million tokens?: Gemini 2.5 Flash: $0.3 per million input tokens and $2.5 per million output tokens. Gemini 3.1 Pro: $2 input and $12 output. These are published list rates as of August 2026, excluding cached, batch and long-context tiers.
What does a million tasks cost on Gemini 2.5 Flash vs Gemini 3.1 Pro?: At the same fixed profile, one million tasks cost $5,100 on Gemini 2.5 Flash and $27,000 on Gemini 3.1 Pro. The gap comes entirely from list-price differences, not from any difference in the work done.