Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or GPT-5.6 Terra?

Neither: both run at $18 per million tokens, three parts input to one part output, read on 16 Sept 2026.

Where is each one cheapest?

Gemini 3.1 Pro Preview Custom Tools: nobody goes below the maker's own price with a reason we can point at, so $18 is the number to beat. GPT-5.6 Terra: nobody goes below the maker's own price with a reason we can point at, so $18 is the number to beat.

Can I buy both from one provider?

Yes. 9 providers sell both: Kilo Gateway, LLMTR, Merge Gateway, NanoGPT, Nous Portal, OpenRouter, and more. The cheapest of them for the two together is Kilo Gateway.

Which holds more context?

GPT-5.6 Terra, at 1.1M tokens against 1M.

Gemini 3.1 Pro Preview Custom Tools vs GPT-5.6 Terra.

model vs model · prices as of 16 Sept 2026

GPT-5.6 Terra takes 1 of 5 rounds against Gemini 3.1 Pro Preview Custom Tools. Both cost $18 per million tokens to run.

Google

Gemini 3.1 Pro Preview Custom Tools

$18/M tokens

Google list price, nothing below it is accounted for · $1.92 per 1,000 pages

1M context · tool calling · reads images

OpenAIwins 1 rounds

GPT-5.6 Terra

$18/M tokens

OpenAI list price, nothing below it is accounted for · $1.92 per 1,000 pages

1.1M context · tool calling · reads images

List price in (lower wins)

$2/M

List price out (lower wins)

$12/M

Cheapest we can explain (lower wins)

none below list

Standard price (lower wins)

$18/M

Cost per 1,000 pages (lower wins)

$1.92

Context

1M tokens

1.1M tokens

Open weights

Tool calling

yes

Structured output

yes

Reads images

yes

Reasoning

yes

Released

19 Feb 2026

9 Jul 2026

Providers selling it

Price we measure against

the maker's own

Trains on your prompts (no is better)

no provider to check

Providers selling both · 9

Kilo Gateway$18 / $18
LLMTR$18 / $18
Merge Gateway$18 / $18
NanoGPT$18 / $18
Nous Portal$18 / $18
OpenRouter$18 / $18
OrcaRouter$18 / $18
Eden AI$18 / $19.80

Gemini 3.1 Pro Preview Custom Tools then GPT-5.6 Terra, per million tokens · showing the 8 cheapest of 9

Go further

open in the compare tool →every price for Gemini 3.1 Pro Preview Custom Tools every price for GPT-5.6 Terra

Add a third or fourth model, or switch the weighting, in the tool.

What moved in the last seven days

Gemini 3.1 Pro Preview Custom ToolsNous Portal$1.60 / $9.60 $2 / $1225% dearer · 16 Sept 2026
GPT-5.6 TerraNous Portal$1.60 / $9.60 $2 / $1225% dearer · 16 Sept 2026
GPT-5.6 TerraRequesty$2 / $12 $2.20 / $13.2010% dearer · 16 Sept 2026
GPT-5.6 TerraCortecs$2.30 / $13.81 $2.28 / $13.671.0% cheaper · 11 Sept 2026

Frequently asked

Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or GPT-5.6 Terra?: Neither: both run at $18 per million tokens, three parts input to one part output, read on 16 Sept 2026.
Where is each one cheapest?: Gemini 3.1 Pro Preview Custom Tools: nobody goes below the maker's own price with a reason we can point at, so $18 is the number to beat. GPT-5.6 Terra: nobody goes below the maker's own price with a reason we can point at, so $18 is the number to beat.
Can I buy both from one provider?: Yes. 9 providers sell both: Kilo Gateway, LLMTR, Merge Gateway, NanoGPT, Nous Portal, OpenRouter, and more. The cheapest of them for the two together is Kilo Gateway.
Which holds more context?: GPT-5.6 Terra, at 1.1M tokens against 1M.

Prices exclude tax and are per million tokens, read 16 Sept 2026 from each provider's own catalog. The standard price blends three parts input to one part output; a page is 600 tokens in and 60 out. Bars are scaled to the larger value in each row.