Gemini 3.1 Pro vs Gemini 3.1 Pro Preview Custom Tools: API Cost Comparison
Compare the API pricing, context windows, features, and real-world cost projections for Gemini 3.1 Pro (Google) and Gemini 3.1 Pro Preview Custom Tools (Google). Use the interactive calculator below to compute your exact monthly cost based on your token usage and request volume.
Prices verified Mar 27, 2026
Interactive Cost Calculator
Fills in typical token counts for a workload type
Tokens in each prompt sent to the model
Tokens generated in each response
Total API calls per month
Showing costs for 2 models. Cheapest: Gemini 3.1 Pro at $80.00/month.
| Alert | |||||||
|---|---|---|---|---|---|---|---|
BestGemini 3.1 Pro | $80.00 | $0.008000 | $20.00 | $60.00 | — | Alerts coming soon | |
Gemini 3.1 Pro Preview Custom Tools | $80.00 | $0.008000 | $20.00 | $60.00 | — | Alerts coming soon |
Monthly Cost Comparison
Price Comparison at a Glance
All prices are in USD per 1 million tokens ($/M tokens). Lower is cheaper.
| Pricing Type | Gemini 3.1 Pro | Gemini 3.1 Pro Preview Custom Tools | Cheaper |
|---|---|---|---|
| Input (standard) | $2.00/M | $2.00/M | — |
| Output | $12.00/M | $12.00/M | — |
| Cached input | $0.20/M | N/A | — |
| Batch input | $1.00/M | N/A | — |
| Batch output | $6.00/M | N/A | — |
Prices last verified: 2026-03-08 – 2026-03-27
Cost Breakdown by Usage Volume
Estimated monthly costs at different request volumes, assuming 1,000 input tokens and 500 output tokens per request. Adjust in the calculator above for your specific use case.
| Volume | Gemini 3.1 ProMonthly | Gemini 3.1 Pro Preview Custom ToolsMonthly | Gemini 3.1 ProPer request | Gemini 3.1 Pro Preview Custom ToolsPer request |
|---|---|---|---|---|
| 1K requests/mo | $8.00 | $8.00 | $0.008000 | $0.008000 |
| 10K requests/mo | $80.00 | $80.00 | $0.008000 | $0.008000 |
| 100K requests/mo | $800.00 | $800.00 | $0.008000 | $0.008000 |
| 1M requests/mo | $8,000.00 | $8,000.00 | $0.008000 | $0.008000 |
Green values indicate the lower-cost option at each volume tier. Cost per request is calculated at 1,000 input + 500 output tokens using standard (non-batch, non-cached) pricing.
Price History
Input price per 1M tokensWhen to Choose Gemini 3.1 Pro
by Google
- Document summarization
- RAG / Semantic search
- Code generation
Input / 1M tokens
$2.00/M
Output / 1M tokens
$12.00/M
Context window
2,097,152
Tier
premium
When to Choose Gemini 3.1 Pro Preview Custom Tools
by Google
- General chatbot
Input / 1M tokens
$2.00/M
Output / 1M tokens
$12.00/M
Context window
1,048,576
Tier
mid
Key Differences Beyond Price
Cost is only one factor in choosing an AI model. Context window size, rate limits, supported features, and latency all affect whether a model fits your use case.
| Capability | Gemini 3.1 Pro | Gemini 3.1 Pro Preview Custom Tools |
|---|---|---|
| Context window | 2,097,152 tokens | 1,048,576 tokens |
| Max output tokens | 65,536 tokens | 65,536 tokens |
| Performance tier | Premium | Mid |
| Vision / image input | Yes | Yes |
| Function calling | Yes | Yes |
| JSON mode | Yes | Yes |
| Prompt caching | Yes | No |
| Batch API (50% discount) | Yes | No |
| Extended reasoning | Yes | No |
| Fine-tuning | No | No |
| Rate limit (req/min) | 1,000 | Not published |
Gemini 3.1 Pro notes
Preview model. Tiered pricing: prompts over 200K tokens billed at $4.00 input / $18.00 output.
Frequently Asked Questions
Is Gemini 3.1 Pro cheaper than Gemini 3.1 Pro Preview Custom Tools?
Gemini 3.1 Pro and Gemini 3.1 Pro Preview Custom Tools cost the same at standard usage (1,000 input + 500 output tokens, 100K requests/month): $800.00/month each. For different token ratios, use the calculator above.
Which model has a larger context window, Gemini 3.1 Pro or Gemini 3.1 Pro Preview Custom Tools?
Gemini 3.1 Pro has a larger context window at 2,097,152 tokens, compared to 1,048,576 tokens for Gemini 3.1 Pro Preview Custom Tools. A larger context window is important for processing long documents, multi-turn conversations, or large codebases without truncation.
Do Gemini 3.1 Pro and Gemini 3.1 Pro Preview Custom Tools support the Batch API?
Gemini 3.1 Pro supports the Batch API (50% discount for async processing), while Gemini 3.1 Pro Preview Custom Tools does not. If your workload tolerates up to 24-hour latency, routing to Gemini 3.1 Pro with batch pricing could significantly cut costs versus Gemini 3.1 Pro Preview Custom Tools's standard rate.
Which model offers better prompt caching?
Gemini 3.1 Pro supports prompt caching at $0.20/M for cached input, while Gemini 3.1 Pro Preview Custom Tools does not offer prompt caching. For RAG applications or chatbots with large, repeated context, Gemini 3.1 Pro's caching capability can substantially reduce effective costs.
What are the best use cases for Gemini 3.1 Pro vs Gemini 3.1 Pro Preview Custom Tools?
Gemini 3.1 Pro is best suited for Document summarization, RAG / Semantic search, Code generation, while Gemini 3.1 Pro Preview Custom Tools is optimized for General chatbot. Choose based on which use case matches your primary workload — and validate with the cost calculator above to confirm the total monthly spend fits your budget.
What is the cost per request for Gemini 3.1 Pro vs Gemini 3.1 Pro Preview Custom Tools?
At 1,000 input tokens and 500 output tokens per request — a typical conversational workload — Gemini 3.1 Pro costs $0.008000 per request and Gemini 3.1 Pro Preview Custom Tools costs $0.008000 per request. At 100,000 requests/month, that translates to $800.00 and $800.00 respectively. Use the interactive calculator to adjust these parameters for your actual workload.
Gemini 3.1 Pro vs Gemini 3.1 Pro Preview Custom Tools: Summary
When comparing Gemini 3.1 Pro and Gemini 3.1 Pro Preview Custom Tools for API cost, the right choice depends on your workload's token profile, required features, and tolerance for latency. Both models cost the same at standard usage volumes (1,000 input + 500 output tokens per request at 100,000 requests/month) at $800.00/month.
Both models are priced in USD per million tokens, the standard unit across all major AI API providers. Gemini 3.1 Pro charges $2.00/M for input tokens and $12.00/M for output tokens. Gemini 3.1 Pro Preview Custom Tools charges $2.00/M input and $12.00/M output. If your workload is output-heavy (more tokens generated than consumed as input), the model with the lower output price compounds cost savings significantly at scale.
Prompt caching is supported by Gemini 3.1 Pro but not Gemini 3.1 Pro Preview Custom Tools. For workloads with large, repeated system prompts or document context — such as RAG pipelines or multi-turn conversations with a fixed knowledge base — prompt caching can reduce effective input costs by 60–90%, which may change the cost ranking between these two models at your specific usage pattern.
Context window capacity differs between the two: Gemini 3.1 Pro supports up to 2,097,152 tokens in a single request, versus 1,048,576 tokens for Gemini 3.1 Pro Preview Custom Tools. A larger context window is essential for document summarization, large codebase analysis, and multi-document retrieval-augmented generation (RAG) applications.
Use the interactive calculator at the top of this page to enter your actual token usage and monthly request volume for a precise cost comparison tailored to your workload. Adjust for batch API discounts and prompt caching to find the most cost-effective option for your specific deployment.
Related Comparisons
Explore other model comparisons from the same providers or performance tiers.
Related Provider Pages
View complete pricing tables and model lineups for the providers behind these models.
Relevant Use Cases
See cost recommendations for workloads where Gemini 3.1 Pro or Gemini 3.1 Pro Preview Custom Tools is recommended.