Gemini 3.1 Pro vs GPT-5.6 Luna: pricing and benchmarks
GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 90% cheaper on output tokens ($1.20 vs $12.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $1,160 for Gemini 3.1 Pro, 90% less. Roughly tied. Gemini 3.1 Pro scores 155.0 and GPT-5.6 Luna scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
Prices verified September 14, 2026.
Which should you choose?
Roughly tied. Gemini 3.1 Pro scores 155.0 and GPT-5.6 Luna scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
GPT-5.6 Luna scores 67.2% on DeepSWE vs 11.7% for Gemini 3.1 Pro.
GPT-5.6 Luna scores 82.1% on FrontierMath (Tiers 1–3) vs 59.6% for Gemini 3.1 Pro.
GPT-5.6 Luna costs $0.45 per 1M tokens (3:1 input-to-output mix) vs $4.50 for Gemini 3.1 Pro, 90% less.
GPT-5.6 Luna delivers equal or higher overall capability for 90% less.
Pricing and specs
| Gemini 3.1 Pro | GPT-5.6 Luna | |
|---|---|---|
| Provider | OpenAI | |
| API model ID | gemini-3.1-pro-preview | gpt-5.6-luna |
| Input / 1M tokens | $2.00 | $0.20 |
| Cached input / 1M tokens | $0.20 | $0.02 |
| Output / 1M tokens | $12.00 | $1.20 |
| Long-context rates | $4.00 in / $18.00 out above 200K prompt tokens | $0.40 in / $1.80 out on long-context requests |
| Context window | 1.05M tokens | 1.05M tokens |
| Max output | 66K tokens | 128K tokens |
| Batch discount | — | 50% off |
Benchmarks
| Gemini 3.1 Pro | GPT-5.6 Luna | |
|---|---|---|
| Epoch Capabilities Index | 155.0 | 156.3 |
| GPQA Diamond· Science reasoning | 92.6% | 88.8% |
| FrontierMath (Tiers 1–3)· Advanced math | 59.6% | 82.1% |
| SimpleQA Verified· Factual accuracy | 73.5% | 41.0% |
| ARC-AGI-2· Abstract reasoning | 77.1% | 59.5% |
| DeepSWE· Coding | 11.7% | 67.2% |
| APEX-Agents· Agentic work | 33.5% | — |
Source: Epoch AI, best recorded result per model (CC BY 4.0). A dash means no published score. See all benchmarks
Monthly cost for real workloads
| Workload | Gemini 3.1 Pro | GPT-5.6 Luna | Difference |
|---|---|---|---|
Support chatbot 100,000 replies a month, ~1,500 input tokens (system prompt + history) and ~400 output tokens each. | $780.00 | $78.00 | GPT-5.6 Luna 90% cheaper |
Document Q&A (RAG) 50,000 questions a month with ~8,000 tokens of retrieved context and ~600 output tokens each. | $1,160 | $116.00 | GPT-5.6 Luna 90% cheaper |
Coding agent 10,000 agent steps a month, ~40,000 input tokens each (70% read from the prompt cache) and ~2,000 output tokens. | $536.00 | $53.60 | GPT-5.6 Luna 90% cheaper |
Estimates use standard list prices and ignore cache-write surcharges. Different tokenizers can count the same text differently, so test with your own prompts.
Gemini 3.1 Pro vs GPT-5.6 Luna cost calculator
- $116.00/mo$0.0023 / request
- Gemini 3.1 ProGoogle$1,160/mo$0.02 / request
Standard-tier list prices. Long-context rates apply automatically where the provider publishes a threshold. Excludes cache-write surcharges, taxes, batch and volume discounts.
Gemini 3.1 Pro pricing notes
Google’s Gemini 3.1 Pro model, currently offered as a preview.
- Prompts over 200K tokens are billed at $4 input / $18 output per 1M tokens.
- No free tier on the Gemini API.
- Output price includes thinking tokens.
GPT-5.6 Luna pricing notes
The GPT-5.6 model optimized for cost-sensitive, high-volume workloads.
- Cache writes are billed at $0.25 per 1M tokens.
- Fast mode costs 2x the standard rate; Flex costs half.
Frequently asked questions
- Is Gemini 3.1 Pro cheaper than GPT-5.6 Luna?
- GPT-5.6 Luna is 90% cheaper on input tokens ($0.20 vs $2.00 per 1M). GPT-5.6 Luna is 90% cheaper on output tokens ($1.20 vs $12.00 per 1M). On our document Q&A workload (50,000 questions a month), GPT-5.6 Luna costs $116.00 a month versus $1,160 for Gemini 3.1 Pro, 90% less.
- Which is more capable, Gemini 3.1 Pro or GPT-5.6 Luna?
- Roughly tied. Gemini 3.1 Pro scores 155.0 and GPT-5.6 Luna scores 156.3 on the Epoch Capabilities Index, and their confidence intervals overlap.
- How much does Gemini 3.1 Pro cost per 1M tokens?
- Gemini 3.1 Pro costs $2.00 per 1M input tokens and $12.00 per 1M output tokens, and $0.20 per 1M cached input tokens on Google’s standard tier.
- How much does GPT-5.6 Luna cost per 1M tokens?
- GPT-5.6 Luna costs $0.20 per 1M input tokens and $1.20 per 1M output tokens, and $0.02 per 1M cached input tokens on OpenAI’s standard tier.
- Which has the larger context window, Gemini 3.1 Pro or GPT-5.6 Luna?
- GPT-5.6 Luna has the larger context window: 1.05M tokens versus 1.05M for Gemini 3.1 Pro.