GPT-5.5 vs Gemini 3.5 Flash
OpenAI's flagship against Google's production / efficiency tier — published pricing, context windows and specs, side by side.
GPT-5.5 vs Gemini 3.5 Flash: side-by-side
| GPT-5.5 | Gemini 3.5 Flash | |
|---|---|---|
| Maker | OpenAI | |
| Released | 23 April 2026 | 19 May 2026 (Google I/O) |
| Tier | Flagship | Production / efficiency tier |
| Context window | 1,000,000 tokens (400K in Codex CLI) | 1,048,576 tokens |
| Max output | Not specified | 65,536 tokens |
| API price (per 1M) | $5 / $30 per 1M tokens (Thinking) | $1.50 / $9 per 1M tokens |
| Access | Proprietary — ChatGPT & Codex (Plus, Pro, Business, Enterprise) + API | Proprietary — Gemini API (Google) |
| Best at | Agentic coding, computer use, deep research | Agentic coding, high-volume production work at near-Pro quality |
| Standout | First full retrain since GPT-4.5 — unified multimodal (text, images, audio, video) | Beats Gemini 3.1 Pro on coding at 25% lower cost — first public Gemini 3.5 release |
Price comparison
| Model | Input (per 1M) | Output (per 1M) |
|---|---|---|
| GPT-5.5 (Thinking) | $5.00 | $30.00 |
| GPT-5.5 Pro | $30.00 | $180.00 |
| Gemini 3.5 Flash | $1.50 | $9.00 |
Estimate your monthly API cost for GPT-5.5 vs Gemini 3.5 Flash with the LLM API pricing calculator →
Published benchmark figures
Each figure below is the model's own published score as listed on its AI Model Hub page. Different suites (and suite versions) are not directly comparable.
| Model | Benchmark | Published score |
|---|---|---|
| GPT-5.5 | Terminal-Bench 2.0 | 82.7% |
| GPT-5.5 | GDPval | 84.9% |
| GPT-5.5 | Expert-SWE | 73.1% |
| GPT-5.5 | SWE-bench Pro | 58.6% |
| GPT-5.5 | FrontierMath Tier 4 | 35.4% |
| Gemini 3.5 Flash | Terminal-Bench 2.1 | 76.2% |
| Gemini 3.5 Flash | MCP Atlas | 83.6% |
| Gemini 3.5 Flash | CharXiv Reasoning | 84.2% |
| Gemini 3.5 Flash | GPQA | 82.8% |
What the table says
- Pricing. GPT-5.5 lists at $5 / $30 per 1M tokens (Thinking); Gemini 3.5 Flash lists at $1.50 / $9 per 1M tokens. On these published rates, Gemini 3.5 Flash's input price is 3.3x lower than GPT-5.5's, and Gemini 3.5 Flash's output price is 3.3x lower than GPT-5.5's. GPT-5.5 Pro lists at $30 / $180 per 1M tokens. Cached input for Gemini 3.5 Flash lists at $0.15 per 1M tokens.
- Context. Both are in the same context class: GPT-5.5 lists 1,000,000 tokens (400K in Codex CLI) and Gemini 3.5 Flash lists 1,048,576 tokens.
- Access. Both are proprietary, hosted-API models; neither publishes weights for self-hosting.
- Benchmarks. The two model pages report results on different benchmark suites, so the published scores are not directly comparable head-to-head; the tables below list each model's own published figures.
Key takeaway
Everything above is drawn from the two models' published rate cards and spec sheets. Which one fits depends on the workload you price it against — run your own token volumes through the pricing calculator to see the monthly difference.
Full GPT-5.5 overview Full Gemini 3.5 Flash overview
Frequently asked questions
Which is cheaper, GPT-5.5 or Gemini 3.5 Flash?
Gemini 3.5 Flash — it lists at $1.50 / $9 per 1M tokens versus $5 / $30 per 1M tokens (Thinking) for GPT-5.5.
Which has the bigger context window, GPT-5.5 or Gemini 3.5 Flash?
They are in the same class: GPT-5.5 lists 1,000,000 tokens (400K in Codex CLI) and Gemini 3.5 Flash lists 1,048,576 tokens.
Which model is newer?
Gemini 3.5 Flash is the more recent release (19 May 2026 (Google I/O)); GPT-5.5 was released 23 April 2026.
Can I run GPT-5.5 or Gemini 3.5 Flash locally?
No — both GPT-5.5 and Gemini 3.5 Flash are proprietary models accessed through their vendors' APIs and apps; neither publishes weights.
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