Google: Gemini 3 Flash Preview (batch) vs OpenAI: GPT-5.1-Codex
Head-to-head API pricing and cost comparison between Google’s Google: Gemini 3 Flash Preview (batch) and OpenAI’s OpenAI: GPT-5.1-Codex. Prices auto-refresh daily from OpenRouter.
Google: Gemini 3 Flash Preview (batch) is 80% cheaper for input tokens; Google: Gemini 3 Flash Preview (batch) also wins on output tokens.
Side-by-side comparison
| Spec | Google: Gemini 3 Flash Preview (batch) | OpenAI: GPT-5.1-Codex |
|---|---|---|
| Input price (per 1M) | $0.25 | $1.25 |
| Cached input (per 1M) | — | $0.13 |
| Output price (per 1M) | $1.50 | $10.00 |
| Batch input (per 1M) | — | $0.63 |
| Batch output (per 1M) | — | $5.00 |
| Reasoning price (per 1M) | $1.50 | — |
| Context window | 1049K | 400K |
| Vision support | Yes | Yes |
| Caching support | No | Yes |
| 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 Flash Preview (batch) | OpenAI: GPT-5.1-Codex | Savings |
|---|---|---|---|
1K req/day 500in / 200out tokens | $12.75 | $78.75 | $66.00 Google: Gemini 3 Flash Preview (batch) wins |
10K req/day 1500in / 500out tokens | $337.50 | $2,063 | $1,725 Google: Gemini 3 Flash Preview (batch) wins |
100K req/day 3000in / 800out tokens | $5,850 | $35,250 | $29,400 Google: Gemini 3 Flash Preview (batch) wins |
1M req/day 8000in / 2000out tokens | $150,000 | $900,000 | $750,000 Google: Gemini 3 Flash Preview (batch) wins |
Adjust input/output token counts, request volume, batch & cached pricing.
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Frequently asked questions
Which is cheaper, Google: Gemini 3 Flash Preview (batch) or OpenAI: GPT-5.1-Codex?
For input tokens, Google: Gemini 3 Flash Preview (batch) is roughly 80% cheaper at $0.25/1M vs $1.25/1M. For output tokens, Google: Gemini 3 Flash Preview (batch) wins at $1.50/1M. 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 Flash Preview (batch) has a context window of 1049K tokens. OpenAI: GPT-5.1-Codex offers 400K 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 Flash Preview (batch) or OpenAI: GPT-5.1-Codex?
Choose Google: Gemini 3 Flash Preview (batch) if you’re already on the Google stack, want reasoning capabilities, or prefer its lower input price. Choose OpenAI: GPT-5.1-Codex for OpenAI’s ecosystem, native vision input, or its differentiated capabilities. 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: Aug 28, 2026.