Gemini 3.1 Pro vs Gemini 3.5 Flash: pricing and benchmarks
Gemini 3.5 Flash is 25% cheaper on input tokens ($1.50 vs $2.00 per 1M). Gemini 3.5 Flash is 25% cheaper on output tokens ($9.00 vs $12.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 3.5 Flash costs $870.00 a month versus $1,160 for Gemini 3.1 Pro, 25% less. Roughly tied. Gemini 3.1 Pro scores 155.0 and Gemini 3.5 Flash scores 154.7 on the Epoch Capabilities Index, and their confidence intervals overlap.
Prices verified September 14, 2026.
Which should you choose?
Roughly tied. Gemini 3.1 Pro scores 155.0 and Gemini 3.5 Flash scores 154.7 on the Epoch Capabilities Index, and their confidence intervals overlap.
Gemini 3.5 Flash scores 37.4% on DeepSWE vs 11.7% for Gemini 3.1 Pro.
Gemini 3.5 Flash scores 62.8% on FrontierMath (Tiers 1–3) vs 59.6% for Gemini 3.1 Pro.
Gemini 3.5 Flash costs $3.375 per 1M tokens (3:1 input-to-output mix) vs $4.50 for Gemini 3.1 Pro, 25% less.
Gemini 3.5 Flash delivers statistically similar overall capability for 25% less.
Pricing and specs
| Gemini 3.1 Pro | Gemini 3.5 Flash | |
|---|---|---|
| Provider | ||
| API model ID | gemini-3.1-pro-preview | gemini-3.5-flash |
| Input / 1M tokens | $2.00 | $1.50 |
| Cached input / 1M tokens | $0.20 | $0.15 |
| Output / 1M tokens | $12.00 | $9.00 |
| Long-context rates | $4.00 in / $18.00 out above 200K prompt tokens | — |
| Context window | 1.05M tokens | 1.05M tokens |
| Max output | 66K tokens | 66K tokens |
| Batch discount | — | 50% off |
Benchmarks
| Gemini 3.1 Pro | Gemini 3.5 Flash | |
|---|---|---|
| Epoch Capabilities Index | 155.0 | 154.7 |
| GPQA Diamond· Science reasoning | 92.6% | 90.4% |
| FrontierMath (Tiers 1–3)· Advanced math | 59.6% | 62.8% |
| SimpleQA Verified· Factual accuracy | 73.5% | 66.2% |
| ARC-AGI-2· Abstract reasoning | 77.1% | 72.1% |
| DeepSWE· Coding | 11.7% | 37.4% |
| APEX-Agents· Agentic work | 33.5% | — |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | Gemini 3.1 Pro | Gemini 3.5 Flash | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $780.00 | $585.00 | Gemini 3.5 Flash 25% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $1,160 | $870.00 | Gemini 3.5 Flash 25% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $536.00 | $402.00 | Gemini 3.5 Flash 25% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
Gemini 3.1 Pro vs Gemini 3.5 Flash cost calculator
- $870.00/mo$0.02 / request
- Gemini 3.1 ProGoogle$1,160/mo$0.02 / request
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Gemini 3.1 Pro pricing notes
Google’s Gemini 3.1 Pro model, currently offered as a preview.
- Prompts over 200K tokens are billed at $4 input / $18 output per 1M tokens.
- No free tier on the Gemini API.
- Output price includes thinking tokens.
Gemini 3.5 Flash pricing notes
Google’s Gemini 3.5 Flash model, with thinking, tool use and a 1M-token context window.
- Output price includes thinking tokens.
- Context cache storage costs $1.00 per 1M tokens per hour.
- Priority inference costs 1.8x the standard rate.
Frequently asked questions
- Is Gemini 3.1 Pro cheaper than Gemini 3.5 Flash?
- Gemini 3.5 Flash is 25% cheaper on input tokens ($1.50 vs $2.00 per 1M). Gemini 3.5 Flash is 25% cheaper on output tokens ($9.00 vs $12.00 per 1M). On our document Q&A workload (50,000 questions a month), Gemini 3.5 Flash costs $870.00 a month versus $1,160 for Gemini 3.1 Pro, 25% less.
- Which is more capable, Gemini 3.1 Pro or Gemini 3.5 Flash?
- Roughly tied. Gemini 3.1 Pro scores 155.0 and Gemini 3.5 Flash scores 154.7 on the Epoch Capabilities Index, and their confidence intervals overlap.
- How much does Gemini 3.1 Pro cost per 1M tokens?
- Gemini 3.1 Pro costs $2.00 per 1M input tokens and $12.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Google’s standard tier.
- How much does Gemini 3.5 Flash cost per 1M tokens?
- Gemini 3.5 Flash costs $1.50 per 1M input tokens and $9.00 per 1M output tokens, and $0.15 per 1M cached input tokens on Google’s standard tier.
- Which has the larger context window, Gemini 3.1 Pro or Gemini 3.5 Flash?
- Both offer a 1.05M-token context window.