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. Both ship a 1.05m-token context window. On SWE-bench Verified, GPT-5.5 leads by 4.6 pts. On pricing, Gemini 3.5 Flash costs $1.50/1M input tokens; GPT-5.5 ranges from $5 to $8/1M input tokens by tier. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3.5 Flash is safer overall; choose GPT-5.5 when coding workflow support matters.
Decision scorecard
Local evidence first| Signal | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1.05m | 1.05m |
| Cheapest output | $9/1M tokens | $30/1M tokens |
| Provider routes | 4 tracked | 4 tracked |
| Shared benchmarks | 12 shared | SWE-bench Verified leader |
Decision tradeoffs
- Gemini 3.5 Flash holds a shared-benchmark lead on MCP-Atlas, ahead by 8.3 points.
- 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 holds a shared-benchmark lead on SWE-bench Verified, ahead by 4.6 points.
- 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 route or tier on this page.
Gemini 3.5 Flash
$3,450
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: $8,050. 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 $21/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Provider overlap exists on Vercel AI Gateway and OpenRouter; start route-level A/B tests there.
- 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 | 1.05m | 1.05m |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-01 | 2025-12 |
Pricing and availability
| Pricing attribute | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Input price | $1.50/1M tokens |
|
| Output price | $9/1M tokens |
|
| Providers |
Capabilities
| Capability | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| JSON / 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 3.5 Flash | GPT-5.5 |
|---|---|---|
| SWE-bench Verified | 78.0 | 82.6 |
| SWE-bench Pro | 55.1 | 58.6 |
| Google-Proof Q&A | 92.2 | 93.6 |
| Humanity's Last Exam | 40.2 | 41.4 |
| HumanEval | 92.0 | 94.2 |
| ARC-AGI-2 | 72.1 | 85.0 |
| MCP-Atlas | 83.6 | 75.3 |
| Terminal-Bench 2.0 | 76.2 | 82.7 |
| GeneBench-Pro | 8.1 | 12.0 |
| CursorBench | 49.8 | 46.6 |
| CursorBench | 48.8 | 46.6 |
| MMMU Pro | 88.3 | 88.3 |
Continue comparing
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Last reviewed: 2026-10-07. Data sourced from public model cards and provider documentation.