Gemini 3.1 Pro Preview vs GPT-5.5
Gemini 3.1 Pro Preview (2026) and GPT-5.5 (2026) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview ships a 1m-token context window, while GPT-5.5 ships a 1.05m-token context window. On MMLU PRO, Gemini 3.1 Pro Preview leads by 2.9 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 is safer overall; choose Gemini 3.1 Pro Preview when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview | GPT-5.5 |
|---|---|---|
| Best for | multimodal apps, tool-calling agents, and long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 1.05m |
| Cheapest output | $12/1M tokens | $30/1M tokens |
| Provider routes | 5 tracked | 4 tracked |
| Shared benchmarks | MMLU PRO leader | 13 shared |
Decision tradeoffs
- Gemini 3.1 Pro Preview holds a shared-benchmark lead on MMLU PRO, ahead by 2.9 points.
- Gemini 3.1 Pro Preview has the lower cheapest tracked output price at $12/1M tokens.
- Gemini 3.1 Pro Preview has broader tracked provider coverage for fallback and procurement flexibility.
- Local decision data tags Gemini 3.1 Pro Preview for Coding, RAG, and Agents.
- GPT-5.5 holds a shared-benchmark lead on SWE-bench Verified, ahead by 2 points.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 uniquely exposes Reasoning in local model data.
- Local decision data tags GPT-5.5 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 3.1 Pro Preview
$4,600
Cheapest tracked route/tier: Google AI Studio
GPT-5.5
$11,500
Cheapest tracked route/tier: OpenAI API 0-272K input tokens
Estimated monthly gap: $6,900. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- GPT-5.5 is $18/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- Gemini 3.1 Pro Preview is $18/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Reasoning before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-19 | 2026-04-23 |
| Context window | 1m | 1.05m |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | 2025-01 | 2025-12 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview | GPT-5.5 |
|---|---|---|
| Input price |
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| Output price |
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| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview | GPT-5.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.5 |
|---|---|---|
| MMLU PRO | 91.0 | 88.1 |
| SWE-bench Verified | 80.6 | 82.6 |
| SWE-bench Pro | 54.2 | 58.6 |
| Google-Proof Q&A | 94.3 | 93.6 |
| AIME 2025 | 95.0 | 81.2 |
| Humanity's Last Exam | 51.4 | 41.4 |
| HumanEval | 94.0 | 94.2 |
| ARC-AGI-2 | 77.1 | 85.0 |
| MCP-Atlas | 69.2 | 75.3 |
| Massive Multitask Language Understanding | 98.0 | 92.4 |
| Chatbot Arena | 1493.0 | 1488.0 |
| BrowseComp | 85.9 | 84.4 |
| MMMU Pro | 88.2 | 88.3 |
Deep dive
On shared benchmark coverage, MMLU PRO has Gemini 3.1 Pro Preview at 91.0 and GPT-5.5 at 88.1, with Gemini 3.1 Pro Preview ahead by 2.9 points; SWE-bench Verified has Gemini 3.1 Pro Preview at 80.6 and GPT-5.5 at 82.6, with GPT-5.5 ahead by 2 points; SWE-bench Pro has Gemini 3.1 Pro Preview at 54.2 and GPT-5.5 at 58.6, with GPT-5.5 ahead by 4.4 points. The largest visible gap is 4.4 points on SWE-bench Pro, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on reasoning mode: GPT-5.5. Both models share vision, multimodal input, function calling, and tool use, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Gemini 3.1 Pro Preview lists tiered pricing: 0-200,001t is $2/1M input and $12/1M output; 200,001t+ is $4/1M input and $18/1M output, while GPT-5.5 lists tiered pricing: 0-272K input tokens is $5/1M input and $30/1M output; 272K+ input tokens is $8/1M input and $36/1M output. A 70/30 input-output blend puts Gemini 3.1 Pro Preview lower by about $7.50 per million blended tokens. For tiered rows, this cheapest-track view can understate interactive or fast-lane spend, so compare the tier you will actually use. Availability is 5 providers versus 4, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview when coding workflow support, lower cheapest-tier input-token cost, and broader provider choice are central to the workload. Choose GPT-5.5 when coding workflow support and larger context windows are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, Gemini 3.1 Pro Preview or GPT-5.5?
GPT-5.5 supports 1.05m tokens, while Gemini 3.1 Pro Preview supports 1m tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Gemini 3.1 Pro Preview or GPT-5.5?
Gemini 3.1 Pro Preview lists tiered pricing: 0-200,001t is $2/1M input and $12/1M output; 200,001t+ is $4/1M input and $18/1M output. GPT-5.5 lists tiered pricing: 0-272K input tokens is $5/1M input and $30/1M output; 272K+ input tokens is $8/1M input and $36/1M output. Compare the tier you will actually use; cheap async pricing can overstate savings for interactive workflows. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview or GPT-5.5 open source?
Gemini 3.1 Pro Preview is listed under Proprietary. GPT-5.5 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, Gemini 3.1 Pro Preview or GPT-5.5?
Both Gemini 3.1 Pro Preview and GPT-5.5 expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Gemini 3.1 Pro Preview or GPT-5.5?
Both Gemini 3.1 Pro Preview and GPT-5.5 expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Gemini 3.1 Pro Preview and GPT-5.5?
Gemini 3.1 Pro Preview is available on Google AI Studio, GCP Vertex AI, OpenRouter, Replicate API, and Vercel AI Gateway. GPT-5.5 is available on OpenAI API, OpenRouter, Vercel AI Gateway, and AWS Bedrock. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-06-15. Data sourced from public model cards and provider documentation.