Gemini 3.1 Pro Preview vs GPT-5.5 Pro
Gemini 3.1 Pro Preview (2026) and GPT-5.5 Pro (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 Pro ships a 1.1M-token context window. On Google-Proof Q&A, Gemini 3.1 Pro Preview leads by a hair. On pricing, Gemini 3.1 Pro Preview costs $2/1M input tokens versus $30/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Gemini 3.1 Pro Preview is ~1400% cheaper at $2/1M; pay for GPT-5.5 Pro only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 1.1M |
| Cheapest output | $12/1M tokens | $180/1M tokens |
| Provider routes | 4 tracked | 2 tracked |
| Shared benchmarks | Google-Proof Q&A leader | 2 rows |
Decision tradeoffs
- Gemini 3.1 Pro Preview leads the largest shared benchmark signal on Google-Proof Q&A by 0.7 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 Pro leads the largest shared benchmark signal on SWE-bench Pro by 4.4 points.
- GPT-5.5 Pro has the larger context window for long prompts, retrieval packs, or transcript analysis.
- GPT-5.5 Pro uniquely exposes Reasoning in local model data.
- Local decision data tags GPT-5.5 Pro for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 3.1 Pro Preview
$4,600
Cheapest tracked route: Google AI Studio
GPT-5.5 Pro
$69,000
Cheapest tracked route: OpenAI API
Estimated monthly gap: $64,400. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- GPT-5.5 Pro is $168/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- GPT-5.5 Pro adds Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 3.1 Pro Preview is $168/1M 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 | 1.1M |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-01 | 2025-12 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Input price | $2/1M tokens | $30/1M tokens |
| Output price | $12/1M tokens | $180/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| 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 |
Benchmarks
| Benchmark | Gemini 3.1 Pro Preview | GPT-5.5 Pro |
|---|---|---|
| Google-Proof Q&A | 94.3 | 93.6 |
| SWE-bench Pro | 54.2 | 58.6 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has Gemini 3.1 Pro Preview at 94.3 and GPT-5.5 Pro at 93.6, with Gemini 3.1 Pro Preview ahead by 0.7 points; SWE-bench Pro has Gemini 3.1 Pro Preview at 54.2 and GPT-5.5 Pro at 58.6, with GPT-5.5 Pro 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 Pro. 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 $2/1M input and $12/1M output tokens, while GPT-5.5 Pro lists $30/1M input and $180/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.1 Pro Preview lower by about $70 per million blended tokens. Availability is 4 providers versus 2, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview when coding workflow support, lower input-token cost, and broader provider choice are central to the workload. Choose GPT-5.5 Pro 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 Pro?
GPT-5.5 Pro supports 1.1M 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 Pro?
Gemini 3.1 Pro Preview is cheaper on tracked token pricing. Gemini 3.1 Pro Preview costs $2/1M input and $12/1M output tokens. GPT-5.5 Pro costs $30/1M input and $180/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview or GPT-5.5 Pro open source?
Gemini 3.1 Pro Preview is listed under Proprietary. GPT-5.5 Pro 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 Pro?
Both Gemini 3.1 Pro Preview and GPT-5.5 Pro expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Which is better for multimodal input, Gemini 3.1 Pro Preview or GPT-5.5 Pro?
Both Gemini 3.1 Pro Preview and GPT-5.5 Pro 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 Pro?
Gemini 3.1 Pro Preview is available on Google AI Studio, GCP Vertex AI, OpenRouter, and Replicate API. GPT-5.5 Pro is available on OpenAI API and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-19. Data sourced from public model cards and provider documentation.