API cost decision in 10 seconds

GPT-5.6 Terra Pro (batch) vs Gemini 3.5 Flash (batch)

Pick Gemini 3.5 Flash (batch) for lower cost; pick GPT-5.6 Terra Pro (batch) only if the larger context window matters more.

Page updated: 2026-08-06T14:08:16Z Data confirmed: 2026-08-23T12:07:48Z Prices normalized to USD per 1M tokens Sample workload: 1M input + 500K output

Budget verdict

Pick Gemini 3.5 Flash (batch) for lower cost; pick GPT-5.6 Terra Pro (batch) only if the larger context window matters more.

On the standard 1M input plus 500K output workload, Gemini 3.5 Flash (batch) is estimated at $3 vs $4 for GPT-5.6 Terra Pro (batch), saving $1 (25% lower).

Cost-first pickGemini 3.5 Flash (batch)

Context-first pickGPT-5.6 Terra Pro (batch)

Sample savings$125%

10x traffic gap$10

GPT-5.6 Terra Pro (batch) has more context, but Gemini 3.5 Flash (batch) saves $1 on the standard workload. At 10x that traffic, the same price gap is about $10. Use the calculator below to replace the sample workload with your own token volume.

Cost sensitivity

Workload Sensitivity

Same prices, different token mixes.

Gemini 3.5 Flash (batch) stays cheaper across input-heavy, balanced, and output-heavy sample workloads.

Workload shape	Token mix	Better pick	GPT-5.6 Terra Pro (batch)	Gemini 3.5 Flash (batch)
Input-heavy / RAG	5M input + 500K output	Gemini 3.5 Flash (batch)	$8	$6
Balanced workload	1M input + 1M output	Gemini 3.5 Flash (batch)	$7	$5.25
Output-heavy chatbot	1M input + 5M output	Gemini 3.5 Flash (batch)	$31	$23.25

Cheaper input Gemini 3.5 Flash (batch) $1 vs $0.75 / 1M

Gemini 3.5 Flash (batch) is $0.25 cheaper per 1M input tokens (25% lower; 1.33x difference).

Cheaper output Gemini 3.5 Flash (batch) $6 vs $4.5 / 1M

Gemini 3.5 Flash (batch) is $1.5 cheaper per 1M output tokens (25% lower; 1.33x difference).

Larger context GPT-5.6 Terra Pro (batch) 1.05M vs 1.05M

GPT-5.6 Terra Pro (batch) has 1.42K more context (1x larger).

Sample workload Gemini 3.5 Flash (batch) $4 vs $3

Gemini 3.5 Flash (batch) is $1 cheaper on the standard workload (25% lower).

Estimate your workload cost

Your Workload Cost

Prices are normalized to USD per 1M tokens.

Monthly input tokens Monthly output tokens

GPT-5.6 Terra Pro (batch) Calculating… Estimated API cost

Gemini 3.5 Flash (batch) 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 3.5 Flash (batch) has the lower input price; Gemini 3.5 Flash (batch) has the lower output price; GPT-5.6 Terra Pro (batch) offers the larger context window. For the 1M input plus 500K output sample, Gemini 3.5 Flash (batch) is cheaper for the standard workload.

For a 1M input token plus 500K output token workload, the estimated API cost is $4 for GPT-5.6 Terra Pro (batch) and $3 for Gemini 3.5 Flash (batch).

Best Fit

Choose GPT-5.6 Terra Pro (batch) when you care most about larger context window.

Choose Gemini 3.5 Flash (batch) when you care most about lower input-token price, and lower output-token price.

Decision Notes

On the standard 1M input plus 500K output workload, Gemini 3.5 Flash (batch) is estimated at $3 vs $4 for GPT-5.6 Terra Pro (batch), saving $1 (25% lower).
Gemini 3.5 Flash (batch) is $1 cheaper on the standard workload (25% lower).
Gemini 3.5 Flash (batch) is $0.25 cheaper per 1M input tokens (25% lower; 1.33x difference).
Gemini 3.5 Flash (batch) is $1.5 cheaper per 1M output tokens (25% lower; 1.33x difference).
GPT-5.6 Terra Pro (batch) has 1.42K more context (1x larger).

Head-to-Head Specs

Feature	GPT-5.6 Terra Pro (batch) (OpenAI)	Gemini 3.5 Flash (batch) (Google)
Input Price prompt tokens per 1M	$1	$0.75
Completion Price per 1M tokens	$6	$4.5
Sample Workload Cost 1M input + 500K output	$4	$3
Context Window	1.05M	1.05M
Release Date	2026-07-09	2026-05-19

Use-Case Decision Matrix

Use case	Better pick	Why
Budget-constrained production	Gemini 3.5 Flash (batch)	On the standard 1M input plus 500K output workload, Gemini 3.5 Flash (batch) is estimated at $3 vs $4 for GPT-5.6 Terra Pro (batch), saving $1 (25% lower).
High-volume input processing	Gemini 3.5 Flash (batch)	Lower prompt-token price matters most when prompts, retrieved passages, or documents dominate the bill.
Long responses and chatbots	Gemini 3.5 Flash (batch)	Lower output-token price matters most when assistants generate many completion tokens.
RAG or long-document work	GPT-5.6 Terra Pro (batch)	A larger context window leaves more room for retrieved passages, conversation history, or source files.

Related Alternatives

Same-provider lower-cost swaps

gpt-oss-120b (free) can replace GPT-5.6 Terra Pro (batch) when lower sample workload cost matters most: $0.
gpt-oss-20b (free) can replace GPT-5.6 Terra Pro (batch) when lower sample workload cost matters most: $0.
gpt-oss-20b can replace GPT-5.6 Terra Pro (batch) when lower sample workload cost matters most: $0.1.
gpt-oss-120b can replace GPT-5.6 Terra Pro (batch) when lower sample workload cost matters most: $0.12.

Larger context near this budget

Grok 4.20 Multi-Agent offers 2M context with $2.5 sample workload cost.
Grok 4.20 offers 2M context with $2.5 sample workload cost.
DeepSeek V4 Flash 0731 offers 1.31M context with $0.17 sample workload cost.
DeepSeek V4 Flash Latest offers 1.31M context with $0.11 sample workload cost.

Popular competitors

DeepSeek V4 Flash 0731 · DeepSeek · #1
MiMo-V2.5 · Xiaomi · #2
Hy3 · Tencent · #3
Ox Alpha · stealth · #4

Cheaper alternatives

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Larger context alternatives

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Provider catalogs

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OpenAI catalog

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Google catalog

Check other Google models with comparable pricing, context, or release timing.

Open Google models

GPT-5.6 Terra Pro (batch)

GPT-5.6 Terra Pro is the same underlying model as [GPT-5.6 Terra](https://openrouter.ai/openai/gpt-5.6-terra), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. Learn more in OpenAI's docs: https://developers.openai.com/api/docs/guides/reasoning#reasoning-mode

Gemini 3.5 Flash (batch)

Gemini 3.5 Flash is Google's high-efficiency multimodal model, bringing near-Pro level coding and reasoning at Flash-tier cost and speed. It is highly optimized for coding proficiency and parallel agentic execution...