Google: Gemini 3.1 Pro Preview Custom Tools vs OpenAI: GPT-4o
Head-to-head API pricing and cost comparison between Google’s Google: Gemini 3.1 Pro Preview Custom Tools and OpenAI’s OpenAI: GPT-4o. Prices auto-refresh daily from OpenRouter.
Google: Gemini 3.1 Pro Preview Custom Tools is 20% cheaper for input tokens; OpenAI: GPT-4o wins on output tokens at $10.00/1M.
Side-by-side comparison
| Spec | Google: Gemini 3.1 Pro Preview Custom Tools | OpenAI: GPT-4o |
|---|---|---|
| Input price (per 1M) | $2.00 | $2.50 |
| Cached input (per 1M) | $0.20 | — |
| Output price (per 1M) | $12.00 | $10.00 |
| Batch input (per 1M) | — | $1.25 |
| Batch output (per 1M) | — | $5.00 |
| Reasoning price (per 1M) | $12.00 | — |
| Context window | 1049K | 128K |
| Vision support | Yes | Yes |
| Caching support | Yes | No |
| Batch API | No | Yes |
| Reasoning capability | Yes | No |
Monthly cost at volume
Estimated monthly API spend at common production traffic levels (input/output tokens per request shown).
| Volume | Google: Gemini 3.1 Pro Preview Custom Tools | OpenAI: GPT-4o | Savings |
|---|---|---|---|
1K req/day 500in / 200out tokens | $102.00 | $97.50 | $4.50 OpenAI: GPT-4o wins |
10K req/day 1500in / 500out tokens | $2,700 | $2,625 | $75.00 OpenAI: GPT-4o wins |
100K req/day 3000in / 800out tokens | $46,800 | $46,500 | $300.00 OpenAI: GPT-4o wins |
1M req/day 8000in / 2000out tokens | $1,200,000 | $1,200,000 | $0.00 OpenAI: GPT-4o wins |
Adjust input/output token counts, request volume, batch & cached pricing.
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Frequently asked questions
Which is cheaper, Google: Gemini 3.1 Pro Preview Custom Tools or OpenAI: GPT-4o?
For input tokens, Google: Gemini 3.1 Pro Preview Custom Tools is roughly 20% cheaper at $2.00/1M vs $2.50/1M. For output tokens, OpenAI: GPT-4o wins at $10.00/1M. Real-world cost depends on your input/output ratio — use the calculator to model your actual workload.
What’s the context window difference?
Google: Gemini 3.1 Pro Preview Custom Tools has a context window of 1049K tokens. OpenAI: GPT-4o offers 128K tokens. Larger context windows are valuable for long documents, RAG pipelines, and multi-turn conversations — but they come with higher input-token bills if you fill them every request.
Should I use Google: Gemini 3.1 Pro Preview Custom Tools or OpenAI: GPT-4o?
Choose Google: Gemini 3.1 Pro Preview Custom Tools if you’re already on the Google stack, want reasoning capabilities, or prefer its lower input price. Choose OpenAI: GPT-4o for OpenAI’s ecosystem, native vision input, or its cheaper output tokens. Run a small benchmark on your own prompts before committing — price is only one axis.
How are these prices kept current?
Prices are pulled directly from OpenRouter’s public models API once every 24 hours via a Convex cron job, then normalized to per-1M-token figures. Last refresh: Apr 21, 2026.