Gemini 3.1 Pro vs GPT-5.6 Luna
Gemini 3.1 Pro and GPT-5.6 Luna are both current production-tier models. GPT-5.6 Luna is meaningfully cheaper at $1 / $6 per 1M. Gemini 3.1 Pro leads on coding, reasoning, general knowledge.
Specs side by side
| Metric | Google Gemini 3.1 Pro | OpenAI GPT-5.6 Luna |
|---|---|---|
| Input price (per 1M) | $2 | $1 |
| Output price (per 1M) | $12 | $6 |
| Context window | 2M tokens | 1.1M tokens |
| Speed tier | balanced | fast |
| Open weights | No | No |
| EU region | Yes | Yes |
| Free tier | No | No |
| Prompt caching | Yes | Yes |
| Vision input | Yes | Yes |
| Extended thinking | Yes | Yes |
When to choose each
Choose Gemini 3.1 Pro if…
- You need 2M context (2× more than GPT-5.6 Luna)
- Coding is central to your workload
- Reasoning is central to your workload
Choose GPT-5.6 Luna if…
- Cost is a priority ($1 / $6 per 1M vs $2 / $12 per 1M)
Benchmark delta
Gemini 3.1 Pro leads on
- Coding
- Reasoning
- General knowledge
- Long-context retrieval
- Multilingual
- Vision
- Tool use
GPT-5.6 Luna leads on
GPT-5.6 Luna has no meaningful benchmark lead in this pair.
FAQ — Gemini 3.1 Pro vs GPT-5.6 Luna
Gemini 3.1 Pro vs GPT-5.6 Luna — which is better?
Gemini 3.1 Pro and GPT-5.6 Luna are both current production-tier models. GPT-5.6 Luna is meaningfully cheaper at $1 / $6 per 1M. Gemini 3.1 Pro leads on coding, reasoning, general knowledge. The right pick depends on your use case — see "When to choose each" above for a data-driven decision.
How does Gemini 3.1 Pro pricing compare to GPT-5.6 Luna?
Gemini 3.1 Pro costs $2 / $12 per 1M vs GPT-5.6 Luna at $1 / $6 per 1M. GPT-5.6 Luna is cheaper on output tokens by roughly 100%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does Gemini 3.1 Pro or GPT-5.6 Luna have the bigger context window?
Gemini 3.1 Pro has a 2M-token context window — 2× the 1.1M context of GPT-5.6 Luna. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for Gemini 3.1 Pro or GPT-5.6 Luna?
Gemini 3.1 Pro: no — Paid-only since 2026-04-01 (previously had free tier via AI Studio). GPT-5.6 Luna: no — Low-cost at $1/$6 per 1M; starter credits only.
Which is better for coding — Gemini 3.1 Pro or GPT-5.6 Luna?
Gemini 3.1 Pro leads on coding benchmarks (Gemini 3.1 Pro: 94/100, GPT-5.6 Luna: 85/100). For production coding agents also weigh tool-use performance — Gemini 3.1 Pro scores 91, GPT-5.6 Luna scores 87.