API cost decision in 10 seconds

DeepSeek V4 Flash (free) vs Gemini 3.1 Pro Preview Custom Tools

Pick DeepSeek V4 Flash (free) for lower cost; pick Gemini 3.1 Pro Preview Custom Tools only if the larger context window matters more.

Page updated: 2026-05-26T10:03:26Z Data confirmed: 2026-05-26T12:43:06Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick DeepSeek V4 Flash (free) 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, DeepSeek V4 Flash (free) is estimated at $0 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $8 (100% lower).

Cost-first pickDeepSeek V4 Flash (free)

Context-first pickGemini 3.1 Pro Preview Custom Tools

Sample savings$8100%

10x traffic gap$80

Gemini 3.1 Pro Preview Custom Tools has more context, but DeepSeek V4 Flash (free) saves $8 on the standard workload. At 10x that traffic, the same price gap is about $80. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

DeepSeek V4 Flash (free) stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	DeepSeek V4 Flash (free)	Gemini 3.1 Pro Preview Custom Tools
Input-heavy / RAG	5M input + 500K output	DeepSeek V4 Flash (free)	$0	$16
Balanced workload	1M input + 1M output	DeepSeek V4 Flash (free)	$0	$14
Output-heavy chatbot	1M input + 5M output	DeepSeek V4 Flash (free)	$0	$62

Cheaper input DeepSeek V4 Flash (free) $0 vs $2 / 1M

DeepSeek V4 Flash (free) is free for input tokens while Gemini 3.1 Pro Preview Custom Tools costs $2 per 1M tokens.

Cheaper output DeepSeek V4 Flash (free) $0 vs $12 / 1M

DeepSeek V4 Flash (free) is free for output tokens while Gemini 3.1 Pro Preview Custom Tools costs $12 per 1M tokens.

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 DeepSeek V4 Flash (free) $0 vs $8

DeepSeek V4 Flash (free) is free for the standard workload while the other model is estimated at $8.

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

DeepSeek V4 Flash (free) 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

DeepSeek V4 Flash (free) has the lower input price; DeepSeek V4 Flash (free) 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, DeepSeek V4 Flash (free) is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $0 for DeepSeek V4 Flash (free) and $8 for Gemini 3.1 Pro Preview Custom Tools.

Best Fit

Choose DeepSeek V4 Flash (free) 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, DeepSeek V4 Flash (free) is estimated at $0 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $8 (100% lower).
DeepSeek V4 Flash (free) is free for the standard workload while the other model is estimated at $8.
DeepSeek V4 Flash (free) is free for input tokens while Gemini 3.1 Pro Preview Custom Tools costs $2 per 1M tokens.
DeepSeek V4 Flash (free) is free for output tokens while Gemini 3.1 Pro Preview Custom Tools costs $12 per 1M tokens.
Gemini 3.1 Pro Preview Custom Tools has 180 more context (1x larger).

Head-to-Head Specs

Feature	DeepSeek V4 Flash (free) (DeepSeek)	Gemini 3.1 Pro Preview Custom Tools (Google)
Input Price prompt tokens per 1M	$0	$2
Completion Price per 1M tokens	$0	$12
Sample Workload Cost 1M input + 500K output	$0	$8
Context Window	1.05M	1.05M
Release Date	2026-04-24	2026-02-25

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	DeepSeek V4 Flash (free)	On the standard 1M input plus 500K output workload, DeepSeek V4 Flash (free) is estimated at $0 vs $8 for Gemini 3.1 Pro Preview Custom Tools, saving $8 (100% lower).
High-volume input processing	DeepSeek V4 Flash (free)	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	DeepSeek V4 Flash (free)	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 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Gemma 4 31B (free) can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Lyria 3 Pro Preview can replace Gemini 3.1 Pro Preview Custom Tools when lower sample workload cost matters most: $0.
Lyria 3 Clip Preview can replace Gemini 3.1 Pro Preview Custom Tools 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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DeepSeek catalog

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Google catalog

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DeepSeek V4 Flash (free)

DeepSeek V4 Flash is an efficiency-optimized Mixture-of-Experts model from DeepSeek with 284B total parameters and 13B activated parameters, supporting a 1M-token context window. It is designed for fast inference and...

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...