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AI Choice Engine

Model comparison

Gemini 3.1 Pro vs GPT-5.5

Google against OpenAI, compared on context, price, and attributed benchmark results.

Recorded profile verification October 1, 2026Individual provider fields may changeEvidence confidence: Medium — see receipts below

Google

Gemini 3.1 Pro

Frontier

vs

OpenAI

GPT-5.5

Frontier

AI model capability comparison
SpecificationGemini 3.1 ProGPT-5.5
ProviderGoogleOpenAI
TierFrontierFrontier
Context window1.05MWinner: 1.05M
Max output66KWinner: 128K
Input / 1M tokensWinner: $2$5
Output / 1M tokensWinner: $12$30
WeightsClosedClosed
ParametersNot verifiedUnverifiedNot verifiedUnverified
Reasoning levelslow, medium, highnone, low, medium, high, xhigh
Modalitiestext, image, video, audio, pdftext, image
API model idgemini-3.1-pro-previewgpt-5.5
ReleasedFebruary 19, 2026April 23, 2026
SWE-bench Verified · source date Gemini 3.1 Pro: 2026-0280.6Not verifiedUnverified
GPQA Diamond · source date Gemini 3.1 Pro: 2026-02, GPT-5.5: 2026-07-27 (comparability not verified)94.393.5
Humanity's Last Exam · source date Gemini 3.1 Pro: 2026-02, GPT-5.5: 2026-04-23 (comparability not verified)44.452.2
Terminal-Bench 2.1 · source date Gemini 3.1 Pro: 2026-07, GPT-5.5: 2026-07-27 (comparability not verified)73.883.4

Dates beside benchmark scores refer to the linked source’s publication or capture date unless that source explicitly states when it measured the result. A shared URL alone does not establish comparable runs; unverified setups are marked. Prices are USD per million tokens at standard rates, excluding batch and caching discounts. Values we could not confirm from the provider are shown as “Not verified” rather than estimated.

Benchmark receipts

Where each score comes from, and how far it can be compared across models.

Pricing tiers

Gemini 3.1 Pro: The current Gemini developer guide lists $2/$12 per MTok below 200K input and $4/$18 above 200K, including thinking output. It leaves the exact 200K boundary unspecified; confirm that boundary and other processing/cache tiers before budgeting. The exact API ID remains gemini-3.1-pro-preview. Restricted Gemini 4 Argon is a separate preview and does not make this endpoint stable.

GPT-5.5: Standard $5/$30 per MTok; prompts above 272K bill 2x input and 1.5x output for the full session in Standard/Batch/Flex. Cached input $0.50; short-context Batch $2.50/$15. Regional/FedRAMP processing adds 10% where eligible.

FrontierRecord checked October 1, 2026

Gemini 3.1 Pro

Gemini 3.1 Pro Preview is Google's multimodal Pro endpoint with a 1,048,576-token input limit and 65,536-token output limit.

Best for

  • Very long documents
  • Multimodal reasoning
  • Frontier knowledge work

Watch out

This API endpoint remains Preview. A separate customtools endpoint is optimized for bash/custom-tool workflows and can behave differently on other tasks. Keep endpoint, thinking level and benchmark version matched; restricted Gemini 4 Argon access is a separate lifecycle.

FrontierRecord checked October 1, 2026

GPT-5.5

OpenAI’s April 2026 model for reasoning, coding and professional work, with a 1.05M-token context. Retained benchmark scores identify their source and configuration.

Best for

  • Reasoning
  • Agentic coding
  • Long-context work

Watch out

An older model, still listed in the API. GPT-5.5 retires from ChatGPT, Work and Codex on October 14, 2026; that notice does not affect the OpenAI API.

When the cheaper one wins

Gemini 3.1 Pro is cheaper on output at $12 per million tokens against $30 for GPT-5.5 — about 2.5×. Use the cheaper tier for classification, extraction, summarisation, and any task where the expensive model’s extra score does not change the accepted output. The expensive one only pays if your hardest task actually fails on the cheap tier. On DeepSWE 1.1, Gemini 3.1 Pro is 11.7% Pass@1 at $2.14/task versus GPT-5.5 at 67% / $7.23/task. This compares standard short-context token rates, not total cost per accepted task. Include input, cache, context tiers, schedules, retries and review in your pilot.

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Evidence confidence: Medium

How strong and complete the evidence behind this comparison is — not a prediction of which model is better.

  • Pricing verified on both sides — Input and output rates are verified for both models.
  • 4/5 core specs verified on both sides — Not published for at least one side: parameter count.
  • No directly aligned benchmark setup — No benchmark has matching cited sources, source dates, units, effort and recorded run details on both models.
  • Verified within the last 90 days — Older of the two catalog checks was 25 days ago.
  • Both models carry source citations — Each side has at least two catalog sources on record.

Source receipts

Each catalog figure was checked against the provider or an independent second source on the date shown.

Related comparisons

Diving deeper on one model? Gemini 3.1 Pro · GPT-5.5

Common questions

Gemini 3.1 Pro vs GPT-5.5

Answered from the verified figures on this page rather than general guidance.

Is Gemini 3.1 Pro or GPT-5.5 cheaper for input?
Gemini 3.1 Pro is cheaper at $2 per million input tokens, against $5 for GPT-5.5 — roughly 2.5× the price. Estimate both input and output token volume for your workload. These are base rates; Gemini 3.1 Pro: The current Gemini developer guide lists $2/$12 per MTok below 200K input and $4/$18 above 200K, including thinking output. It leaves the exact 200K boundary unspecified; confirm that boundary and other processing/cache tiers before budgeting. The exact API ID remains gemini-3.1-pro-preview. Restricted Gemini 4 Argon is a separate preview and does not make this endpoint stable. GPT-5.5: Standard $5/$30 per MTok; prompts above 272K bill 2x input and 1.5x output for the full session in Standard/Batch/Flex. Cached input $0.50; short-context Batch $2.50/$15. Regional/FedRAMP processing adds 10% where eligible.
Is Gemini 3.1 Pro or GPT-5.5 cheaper for output?
Gemini 3.1 Pro is cheaper at $12 per million output tokens, against $30 for GPT-5.5 — roughly 2.5× the price. Estimate both input and output token volume for your workload. These are base rates; Gemini 3.1 Pro: The current Gemini developer guide lists $2/$12 per MTok below 200K input and $4/$18 above 200K, including thinking output. It leaves the exact 200K boundary unspecified; confirm that boundary and other processing/cache tiers before budgeting. The exact API ID remains gemini-3.1-pro-preview. Restricted Gemini 4 Argon is a separate preview and does not make this endpoint stable. GPT-5.5: Standard $5/$30 per MTok; prompts above 272K bill 2x input and 1.5x output for the full session in Standard/Batch/Flex. Cached input $0.50; short-context Batch $2.50/$15. Regional/FedRAMP processing adds 10% where eligible.
Which has the larger context window, Gemini 3.1 Pro or GPT-5.5?
Both accept about 1.05M tokens of context, so document length will not decide between them.
Do Gemini 3.1 Pro and GPT-5.5 support the same reasoning levels?
Gemini 3.1 Pro exposes low, medium, high, while GPT-5.5 exposes none, low, medium, high, xhigh.
Should I use Gemini 3.1 Pro or GPT-5.5?
Both are classified in our frontier tier; this editorial grouping does not imply equal capability. Gemini 3.1 Pro is a candidate for very long documents; GPT-5.5 is a candidate for reasoning. Compare accuracy, tool reliability, latency and cost on representative tasks.

Next step

Choosing between them

The verified figures that separate this pair, computed from the catalog rather than restated boilerplate.

  • Input price: Gemini 3.1 Pro costs $2 per 1M tokens versus $5 for GPT-5.5 — a 2.5x difference at the headline tier.
  • Context: GPT-5.5 takes 1.05M against 1.05M for Gemini 3.1 Pro — only decisive if your prompts approach the smaller window.
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