Gemini 3.1 Pro Preview vs Gemini 3.5 Flash: API Pricing Comparison
Google Gemini 3.1 Pro Preview vs Google Gemini 3.5 Flash — token prices, batch and cache rates, Arena ELO, and cost per request for 8 business use cases. Prices in USD per 1 million tokens. Data snapshot: 2026-08-14.
Gemini 3.1 Pro Preview pricing (Google)
- Input: $2.00 per 1M tokens
- Output: $12.00 per 1M tokens
- Batch API (input/output): $1.00 / $6.00
- Prompt-cache read: $0.20
- Context window: 1M
- Arena ELO: 1480 (as of 2026-08-13)
- Full Gemini 3.1 Pro Preview pricing page
Gemini 3.5 Flash pricing (Google)
- Input: $1.50 per 1M tokens
- Output: $9.00 per 1M tokens
- Batch API (input/output): $0.75 / $4.50
- Prompt-cache read: $0.15
- Context window: 1M
- Arena ELO: 1472 (as of 2026-08-13)
- Full Gemini 3.5 Flash pricing page
Cost per request by business use case
List price vs optimized (prompt caching on the cached input share, batch API for async workloads — only where the provider publishes those rates).
| Use case | Tokens (in/out) | Gemini 3.1 Pro Preview list | Gemini 3.1 Pro Preview optimized | Gemini 3.5 Flash list | Gemini 3.5 Flash optimized |
|---|---|---|---|---|---|
| Support Ticket | 1,500 / 500 | $0.0090 | $0.0074 | $0.0068 | $0.0055 |
| Knowledge Q&A | 2,000 / 800 | $0.014 | $0.011 | $0.010 | $0.0083 |
| Meeting Summary | 10,000 / 1,200 | $0.034 | $0.016 | $0.026 | $0.012 |
| Marketing Content | 2,500 / 1,800 | $0.027 | $0.026 | $0.020 | $0.019 |
| Coding Task | 3,000 / 2,000 | $0.030 | $0.027 | $0.023 | $0.020 |
| Invoice Processing | 1,500 / 600 | $0.010 | $0.0047 | $0.0076 | $0.0036 |
| Call Summary | 2,000 / 700 | $0.012 | $0.0060 | $0.0093 | $0.0045 |
| Agent Workflow | 6,000 / 3,000 | $0.048 | $0.040 | $0.036 | $0.030 |
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These are list prices — real cost also depends on caching, batching, negotiated discounts, marketplace agreements, and existing contracts. Get a FinOps review from OptimNow or compare all models.