Gemini 3.5 Flash vs GPT-5.5
Gemini 3.5 Flash (2026) and GPT-5.5 (2026) are frontier-tier reasoning models from Google DeepMind and OpenAI. Gemini 3.5 Flash ships a 1M-token context window, while GPT-5.5 ships a 1.1M-token context window. On pricing, Gemini 3.5 Flash costs $1.5/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
Gemini 3.5 Flash is ~233% cheaper at $1.5/1M; pay for GPT-5.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1M | 1.1M |
| Cheapest output | $9/1M tokens | $30/1M tokens |
| Provider routes | 2 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 3.5 Flash has the lower cheapest tracked output price at $9/1M tokens.
- Local decision data tags Gemini 3.5 Flash for Coding, RAG, and Agents.
- GPT-5.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- 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 prices on this page.
Gemini 3.5 Flash
$3,450
Cheapest tracked route: Google AI Studio
GPT-5.5
$11,500
Cheapest tracked route: OpenAI API
Estimated monthly gap: $8,050. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.5 Flash and GPT-5.5; plan for SDK, billing, or endpoint changes.
- GPT-5.5 is $21/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- No overlapping tracked provider route is sourced for GPT-5.5 and Gemini 3.5 Flash; plan for SDK, billing, or endpoint changes.
- Gemini 3.5 Flash is $21/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-19 | 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 3.5 Flash | GPT-5.5 |
|---|---|---|
| Input price | $1.5/1M tokens | $5/1M tokens |
| Output price | $9/1M tokens | $30/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint is close: both models cover vision, multimodal input, reasoning mode, function calling, and tool use. That makes context budget, benchmark fit, and provider maturity more important than a simple checklist. If your application depends on one integration detail, verify it against the provider route you plan to use, not just the base model listing.
For cost, Gemini 3.5 Flash lists $1.5/1M input and $9/1M output tokens, while GPT-5.5 lists $5/1M input and $30/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.5 Flash lower by about $8.75 per million blended tokens. Availability is 2 providers versus 2, so concentration risk also matters.
Choose Gemini 3.5 Flash when coding workflow support and lower input-token cost 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. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency.
FAQ
Which has a larger context window, Gemini 3.5 Flash or GPT-5.5?
GPT-5.5 supports 1.1M tokens, while Gemini 3.5 Flash 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 3.5 Flash or GPT-5.5?
Gemini 3.5 Flash is cheaper on tracked token pricing. Gemini 3.5 Flash costs $1.5/1M input and $9/1M output tokens. GPT-5.5 costs $5/1M input and $30/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.5 Flash or GPT-5.5 open source?
Gemini 3.5 Flash 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 3.5 Flash or GPT-5.5?
Both Gemini 3.5 Flash 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 3.5 Flash or GPT-5.5?
Both Gemini 3.5 Flash 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. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run Gemini 3.5 Flash and GPT-5.5?
Gemini 3.5 Flash is available on Google AI Studio and GCP Vertex AI. GPT-5.5 is available on OpenAI API and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-19. Data sourced from public model cards and provider documentation.