API cost decision in 10 seconds

🔥Gemini 3 Flash Preview vs Gemini 3.1 Pro Preview Custom Tools

Pick Gemini 3 Flash Preview for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.

Page updated: 2026-05-26T12:03:47Z Data confirmed: 2026-05-26T14:08:03Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Gemini 3 Flash 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 Flash Preview is estimated at $2 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $6 (75% lower).

Cost-first pickGemini 3 Flash Preview

Context-first pickGemini 3.1 Pro Preview Custom Tools

Sample savings$675%

10x traffic gap$60

Gemini 3.1 Pro Preview Custom Tools has more context, but Gemini 3 Flash Preview saves $6 on the standard workload. At 10x that traffic, the same price gap is about $60. 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 Flash Preview stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	Gemini 3 Flash Preview	Gemini 3.1 Pro Preview Custom Tools
Input-heavy / RAG	5M input + 500K output	Gemini 3 Flash Preview	$4	$16
Balanced workload	1M input + 1M output	Gemini 3 Flash Preview	$3.5	$14
Output-heavy chatbot	1M input + 5M output	Gemini 3 Flash Preview	$15.5	$62

Cheaper input Gemini 3 Flash Preview $0.5 vs $2 / 1M

Gemini 3 Flash Preview is $1.5 cheaper per 1M input tokens (75% lower; 4x difference).

Cheaper output Gemini 3 Flash Preview $3 vs $12 / 1M

Gemini 3 Flash Preview is $9 cheaper per 1M output tokens (75% lower; 4x 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 Flash Preview $2 vs $8

Gemini 3 Flash Preview is $6 cheaper on the standard workload (75% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

Gemini 3 Flash 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 Flash Preview has the lower input price; Gemini 3 Flash 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 Flash Preview is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $2 for Gemini 3 Flash Preview and $8 for Gemini 3.1 Pro Preview Custom Tools.

Best Fit

Choose Gemini 3 Flash 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 Flash Preview is estimated at $2 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $6 (75% lower).
Gemini 3 Flash Preview is $6 cheaper on the standard workload (75% lower).
Gemini 3 Flash Preview is $1.5 cheaper per 1M input tokens (75% lower; 4x difference).
Gemini 3 Flash Preview is $9 cheaper per 1M output tokens (75% lower; 4x difference).
Gemini 3.1 Pro Preview Custom Tools has 180 more context (1x larger).

Head-to-Head Specs

Feature	🔥Gemini 3 Flash Preview (Google)	Gemini 3.1 Pro Preview Custom Tools (Google)
Input Price prompt tokens per 1M	$0.5	$2
Completion Price per 1M tokens	$3	$12
Sample Workload Cost 1M input + 500K output	$2	$8
Context Window	1.05M	1.05M
Release Date	2025-12-17	2026-02-25
Popularity	#7

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Gemini 3 Flash Preview	On the standard 1M input plus 500K output workload, Gemini 3 Flash Preview is estimated at $2 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $6 (75% lower).
High-volume input processing	Gemini 3 Flash Preview	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Gemini 3 Flash 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 Flash Preview when lower sample workload cost matters most: $0.
Gemma 4 31B (free) can replace Gemini 3 Flash Preview when lower sample workload cost matters most: $0.
Lyria 3 Pro Preview can replace Gemini 3 Flash Preview when lower sample workload cost matters most: $0.
Lyria 3 Clip Preview can replace Gemini 3 Flash 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

DeepSeek V4 Flash · DeepSeek · #1
Hy3 preview · Tencent · #2
Claude Opus 4.7 · Anthropic · #3
Claude Sonnet 4.6 · Anthropic · #4

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 Pro Preview Custom Tools

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