Choose Google: Gemini 2.5 Pro if…
- you need audio input — to take speech or audio directly; OpenAI: GPT-6.1 Terra Pro does not advertise it
Google: Gemini 2.5 Pro vs OpenAI: GPT-6.1 Terra Pro
Neither wins outright: Google: Gemini 2.5 Pro is the pick when you need audio input, OpenAI: GPT-6.1 Terra Pro when cost matters at scale.
Key numbers
| Spec | Google: Gemini 2.5 Pro | OpenAI: GPT-6.1 Terra Pro |
|---|---|---|
| Provider | OpenAI | |
| Input price (per 1M tokens) | $1.25 | $1.00 |
| Output price (per 1M tokens) | $10.00 | $5.00 |
| Blended price (3:1 input/output) | $3.44 | $2.00 |
| Cheaper than … of all models we track | 18% | 25% |
| Context window | 1.0M tokens (~1,573 pages) | 1.1M tokens (~1,575 pages) |
| Larger context than … of all models | 80% | 92% |
| Max output per response | 66K tokens (~49,200 words) | 128K tokens (~96,000 words) |
| Input types | text, image, file, audio, video | file, image, text |
| Output types | text | text |
| Free variant | No | No |
| Listed since | 2025-06-17 | 2026-10-26 |
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What it costs for real workloads
Monthly cost at list price for five common workloads. Token counts per unit are stated so you can scale them to your own traffic. A workload that does not fit a model's context window is marked rather than priced.
| Workload (per month) | Google: Gemini 2.5 Pro | OpenAI: GPT-6.1 Terra Pro | Difference |
|---|---|---|---|
| Customer-support chatbot 50,000 conversations — each a 6-turn conversation (1,500 in / 400 out tokens) | $294 | $175 | OpenAI: GPT-6.1 Terra Pro saves $119 |
| RAG search over documents 20,000 questions — each a question answered from ~8 retrieved passages (6,000 in / 500 out tokens) | $250 | $170 | OpenAI: GPT-6.1 Terra Pro saves $80.00 |
| Coding / tool-using agent 2,000 tasks — each a multi-step task with tool calls and file context (60,000 in / 6,000 out tokens) | $270 | $180 | OpenAI: GPT-6.1 Terra Pro saves $90.00 |
| Batch summarisation 10,000 documents — each a 6,000-word report summarised to a page (8,000 in / 600 out tokens) | $160 | $110 | OpenAI: GPT-6.1 Terra Pro saves $50.00 |
| Long-document analysis 500 documents — each a 150-page contract or codebase read in one pass (100,000 in / 2,000 out tokens) | $72.50 | $55.00 | OpenAI: GPT-6.1 Terra Pro saves $17.50 |
Capabilities side by side
| Capability | Google: Gemini 2.5 Pro | OpenAI: GPT-6.1 Terra Pro | What it lets you do |
|---|---|---|---|
| Tool / function calling | ✓ Yes | ✓ Yes | call your APIs and run agent loops |
| Structured output (JSON schema) | ✓ Yes | ✓ Yes | return JSON that validates against your schema |
| Reasoning / thinking mode | ✓ Yes | ✓ Yes | spend extra tokens thinking before answering hard problems |
| Image input | ✓ Yes | ✓ Yes | read screenshots, charts and scanned pages |
| Audio input | ✓ Yes | — | take speech or audio directly |
| File / PDF input | ✓ Yes | ✓ Yes | accept documents without your own parsing step |
| Image output | — | — | generate images, not just text |
| Built-in web search | ✓ Yes | ✓ Yes | answer from live web results |
| Seed (reproducible sampling) | ✓ Yes | ✓ Yes | repeat a generation for tests and evals |
| Log-probabilities | — | — | read token confidence for classification and scoring |
From each model's published parameters and input/output types. “—” means not advertised, not proven absent.
Price history
- Google: Gemini 2.5 Pro: price unchanged since we started tracking it on 2026-03-10.
- OpenAI: GPT-6.1 Terra Pro: price unchanged since we started tracking it on 2026-10-27.
Which should you choose?
Choose OpenAI: GPT-6.1 Terra Pro if…
- cost matters at scale — it is 42% cheaper on a typical 3:1 input/output mix ($175 vs $294 a month for 50,000 support chats)
- you generate long outputs in one go — up to 128K tokens (about 96,000 words) per response
- you want the newer model — released 2026-10-26, 17 months after the other
Frequently asked questions
Is Google: Gemini 2.5 Pro better than OpenAI: GPT-6.1 Terra Pro?
Neither wins outright: Google: Gemini 2.5 Pro is the pick when you need audio input, OpenAI: GPT-6.1 Terra Pro when cost matters at scale. In short: Google: Gemini 2.5 Pro when you need audio input; OpenAI: GPT-6.1 Terra Pro when cost matters at scale, you generate long outputs in one go, you want the newer model.
Which is cheaper, Google: Gemini 2.5 Pro or OpenAI: GPT-6.1 Terra Pro?
OpenAI: GPT-6.1 Terra Pro is cheaper: $2.00 vs $3.44 per 1M tokens at a typical 3:1 input/output mix, 42% less. For 50,000 support conversations a month that is $175 against $294.
How much do Google: Gemini 2.5 Pro and OpenAI: GPT-6.1 Terra Pro cost per million tokens?
Google: Gemini 2.5 Pro costs $1.25 per 1M input tokens and $10.00 per 1M output tokens; OpenAI: GPT-6.1 Terra Pro costs $1.00 input and $5.00 output. Output tokens are billed separately, so long answers shift the gap.
Which has the bigger context window, Google: Gemini 2.5 Pro or OpenAI: GPT-6.1 Terra Pro?
OpenAI: GPT-6.1 Terra Pro: 1.1M tokens, about 1,575 pages, against 1.0M (about 1,573 pages) for Google: Gemini 2.5 Pro.
Do Google: Gemini 2.5 Pro and OpenAI: GPT-6.1 Terra Pro support function calling and JSON output?
Tool calling — Google: Gemini 2.5 Pro: yes, OpenAI: GPT-6.1 Terra Pro: yes. JSON-schema structured output — Google: Gemini 2.5 Pro: yes, OpenAI: GPT-6.1 Terra Pro: yes.
Can Google: Gemini 2.5 Pro or OpenAI: GPT-6.1 Terra Pro read images?
Yes, both accept image input.
Is Google: Gemini 2.5 Pro or OpenAI: GPT-6.1 Terra Pro free to use?
No free variant is listed for either; both are pay-per-token.
What is the maximum output length of Google: Gemini 2.5 Pro and OpenAI: GPT-6.1 Terra Pro?
Google: Gemini 2.5 Pro can write up to 66K tokens (about 49,200 words) per response; OpenAI: GPT-6.1 Terra Pro up to 128K (about 96,000 words).
When were Google: Gemini 2.5 Pro and OpenAI: GPT-6.1 Terra Pro released?
Google: Gemini 2.5 Pro was listed on 2025-06-17; OpenAI: GPT-6.1 Terra Pro on 2026-10-26.
About the two models
Google: Gemini 2.5 Pro
Gemini 2.5 Pro is Google’s state-of-the-art AI model designed for advanced reasoning, coding, mathematics, and scientific tasks. It employs “thinking” capabilities, enabling it to reason through responses with enhanced accuracy...
Full Google: Gemini 2.5 Pro specs →OpenAI: GPT-6.1 Terra Pro
GPT-6.1 Terra Pro is the same underlying model as [GPT-6.1 Terra](https://openrouter.ai/openai/gpt-6.1-terra), served with `reasoning.mode` set to `pro` for higher-quality responses on complex tasks. **Cost note:** pro mode spends far more...
Full OpenAI: GPT-6.1 Terra Pro specs →