GPT-5.6 Luna vs Gemini 3.5 Flash
Detailed comparison of API pricing, technical specifications, and benchmark scores. Updated 2026-06-29.
Cost at a Glance
Gemini 3.5 Flash is 1.5× more expensive than GPT-5.6 Luna (33.3% savings if you switch).
At 5M input + 2M output tokens per month:
Choosing GPT-5.6 Luna could save you $8.50/mo
Price Comparison (per 1M tokens)
| Metric | GPT-5.6 Luna | Gemini 3.5 Flash |
|---|---|---|
| Input (per 1M tokens) | $1.00 | $1.50 |
| Output (per 1M tokens) | $6.00 | $9.00 |
| Cache Write (per 1M tokens) | $1.25 | — |
| Cache Read (per 1M tokens) | $0.10 | $0.15 |
| Batch Input (per 1M tokens) | $0.50 | — |
| Batch Output (per 1M tokens) | $3.00 | — |
Prices are per 1 million tokens. Actual costs depend on your monthly token volume. Use the calculator →
Specifications
| Spec | GPT-5.6 Luna | Gemini 3.5 Flash |
|---|---|---|
| Context Window | 1M | 1M |
| Max Output Tokens | 64K | 64K |
| Knowledge Cutoff | 2026-04 | 2026-04 |
| Modalities | Text | Text, Image |
| Prompt Caching | Yes | Yes |
| Batch API | Yes | No |
| Thinking / Reasoning | No | No |
Benchmark Scores
| Benchmark | GPT-5.6 Luna | Gemini 3.5 Flash |
|---|---|---|
| SWE-bench Verified | 62.5 | 65.0 |
| MMLU-Pro | 79.0 | 80.0 |
| HumanEval | 89.5 | 90.0 |
Benchmark scores from official provider reports. Higher is better. Missing scores indicate the provider has not published that benchmark yet.
Use Cases
GPT-5.6 Luna
Gemini 3.5 Flash
About the Providers
GPT-5.6 Luna is developed by OpenAI. Gemini 3.5 Flash is developed by Google. This is a cross-provider comparison between OpenAI and Google models. For the most up-to-date pricing, always check the official API documentation from each provider.