Gemini 3.1 Pro vs Gemini 3.5 Flash
Detailed comparison of API pricing, technical specifications, and benchmark scores. Updated 2026-06-29.
Cost at a Glance
Gemini 3.1 Pro is 8× more expensive than Gemini 3.5 Flash — switching could save 87.5% on your monthly API bill.
At 5M input + 2M output tokens per month:
Choosing Gemini 3.5 Flash could save you $29.75/mo
Price Comparison (per 1M tokens)
| Metric | Gemini 3.1 Pro | Gemini 3.5 Flash |
|---|---|---|
| Input (per 1M tokens) | $2.00 | $0.25 |
| Output (per 1M tokens) | $12.00 | $1.50 |
| Cache Write (per 1M tokens) | — | — |
| Cache Read (per 1M tokens) | $0.20 | $0.03 |
| Batch Input (per 1M tokens) | — | — |
| Batch Output (per 1M tokens) | — | — |
Prices are per 1 million tokens. Actual costs depend on your monthly token volume. Use the calculator →
Specifications
| Spec | Gemini 3.1 Pro | Gemini 3.5 Flash |
|---|---|---|
| Context Window | 1M | 1M |
| Max Output Tokens | 64K | 64K |
| Knowledge Cutoff | 2026-04 | 2026-04 |
| Modalities | Text, Image, Audio, Video | Text, Image |
| Prompt Caching | Yes | Yes |
| Batch API | No | No |
| Thinking / Reasoning | Yes | No |
Benchmark Scores
| Benchmark | Gemini 3.1 Pro | Gemini 3.5 Flash |
|---|---|---|
| SWE-bench Verified | 80.6 | 65.0 |
| MMLU-Pro | 86.5 | 80.0 |
| HumanEval | 93.5 | 90.0 |
Benchmark scores from official provider reports. Higher is better. Missing scores indicate the provider has not published that benchmark yet.
Use Cases
Gemini 3.1 Pro
Gemini 3.5 Flash
About the Providers
Gemini 3.1 Pro is developed by Google. Gemini 3.5 Flash is developed by Google. Both models are from the same provider, representing different tiers in the Google model lineup. For the most up-to-date pricing, always check the official API documentation from each provider.