API cost decision in 10 seconds

Gemini 3.1 Flash Lite Preview vs Gemini 3.1 Pro Preview Custom Tools

Pick Gemini 3.1 Flash Lite Preview for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.

Pricing data updated: 2026-05-26T11:08:00Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Gemini 3.1 Flash Lite Preview for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.

On the standard 1M input plus 500K output workload, Gemini 3.1 Flash Lite Preview is estimated at $1 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $7 (87.5% lower).

Cost-first pickGemini 3.1 Flash Lite Preview

Context-first pickGemini 3.1 Pro Preview Custom Tools

Sample savings$787.5%

10x traffic gap$70

Gemini 3.1 Pro Preview Custom Tools has more context, but Gemini 3.1 Flash Lite Preview saves $7 on the standard workload. At 10x that traffic, the same price gap is about $70. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Gemini 3.1 Flash Lite Preview stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	Gemini 3.1 Flash Lite Preview	Gemini 3.1 Pro Preview Custom Tools
Input-heavy / RAG	5M input + 500K output	Gemini 3.1 Flash Lite Preview	$2	$16
Balanced workload	1M input + 1M output	Gemini 3.1 Flash Lite Preview	$1.75	$14
Output-heavy chatbot	1M input + 5M output	Gemini 3.1 Flash Lite Preview	$7.75	$62

Cheaper input Gemini 3.1 Flash Lite Preview $0.25 vs $2 / 1M

Gemini 3.1 Flash Lite Preview is $1.75 cheaper per 1M input tokens (87.5% lower; 8x difference).

Cheaper output Gemini 3.1 Flash Lite Preview $1.5 vs $12 / 1M

Gemini 3.1 Flash Lite Preview is $10.5 cheaper per 1M output tokens (87.5% lower; 8x difference).

Larger context Gemini 3.1 Pro Preview Custom Tools 1.05M vs 1.05M

Gemini 3.1 Pro Preview Custom Tools has 180 more context (1x larger).

Sample workload Gemini 3.1 Flash Lite Preview $1 vs $8

Gemini 3.1 Flash Lite Preview is $7 cheaper on the standard workload (87.5% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Gemini 3.1 Flash Lite Preview Calculating… Estimated API cost

Gemini 3.1 Pro Preview Custom Tools Calculating… Estimated API cost

Cheaper for this workload Calculating… Difference: calculating…

This estimate uses normalized public API pricing per 1M tokens. It is a planning aid, not a billing quote. Verify provider pricing, limits, and terms before production use.

Quick Decision

Verdict

Gemini 3.1 Flash Lite Preview has the lower input price; Gemini 3.1 Flash Lite Preview has the lower output price; Gemini 3.1 Pro Preview Custom Tools offers the larger context window. For the 1M input plus 500K output sample, Gemini 3.1 Flash Lite Preview is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $1 for Gemini 3.1 Flash Lite Preview and $8 for Gemini 3.1 Pro Preview Custom Tools.

Best Fit

Choose Gemini 3.1 Flash Lite Preview when you care most about lower input-token price, and lower output-token price.

Choose Gemini 3.1 Pro Preview Custom Tools when you care most about larger context window.

Decision Notes

On the standard 1M input plus 500K output workload, Gemini 3.1 Flash Lite Preview is estimated at $1 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $7 (87.5% lower).
Gemini 3.1 Flash Lite Preview is $7 cheaper on the standard workload (87.5% lower).
Gemini 3.1 Flash Lite Preview is $1.75 cheaper per 1M input tokens (87.5% lower; 8x difference).
Gemini 3.1 Flash Lite Preview is $10.5 cheaper per 1M output tokens (87.5% lower; 8x difference).
Gemini 3.1 Pro Preview Custom Tools has 180 more context (1x larger).

Head-to-Head Specs

Feature	Gemini 3.1 Flash Lite Preview (Google)	Gemini 3.1 Pro Preview Custom Tools (Google)
Input Price prompt tokens per 1M	$0.25	$2
Completion Price per 1M tokens	$1.5	$12
Sample Workload Cost 1M input + 500K output	$1	$8
Context Window	1.05M	1.05M
Release Date	2026-03-03	2026-02-25

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Gemini 3.1 Flash Lite Preview	On the standard 1M input plus 500K output workload, Gemini 3.1 Flash Lite Preview is estimated at $1 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $7 (87.5% lower).
High-volume input processing	Gemini 3.1 Flash Lite Preview	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Gemini 3.1 Flash Lite Preview	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	Gemini 3.1 Pro Preview Custom Tools	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

Gemma 4 26B A4B (free) can replace Gemini 3.1 Flash Lite Preview when lower sample workload cost matters most: $0.
Gemma 4 31B (free) can replace Gemini 3.1 Flash Lite Preview when lower sample workload cost matters most: $0.
Lyria 3 Pro Preview can replace Gemini 3.1 Flash Lite Preview when lower sample workload cost matters most: $0.
Lyria 3 Clip Preview can replace Gemini 3.1 Flash Lite Preview when lower sample workload cost matters most: $0.

Larger context near this budget

Llama 4 Scout offers 10M context with $0.23 sample workload cost.
Grok 4.20 Multi-Agent offers 2M context with $5 sample workload cost.
Grok 4.20 offers 2M context with $2.5 sample workload cost.
GPT-5.4 offers 1.05M context with $10 sample workload cost.

Popular competitors

No popular competitor is currently available.

Cheaper alternatives

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Larger context alternatives

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Provider catalogs

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Google catalog

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Gemini 3.1 Flash Lite Preview

Gemini 3.1 Flash Lite Preview is Google's high-efficiency model optimized for high-volume use cases. It outperforms Gemini 2.5 Flash Lite on overall quality and approaches Gemini 2.5 Flash performance across...

Gemini 3.1 Pro Preview Custom Tools

Gemini 3.1 Pro Preview Custom Tools is a variant of Gemini 3.1 Pro that improves tool selection behavior by preventing overuse of a general bash tool when more efficient third-party...