GPT-6 Luna — Specifications
Compiled by Mustafa Ihsan from the vendor’s published documentation · Last updated
| Developer | OpenAI |
|---|---|
| Type | LLM |
| Modality | Text, vision |
| Parameters | Undisclosed |
| Context window | 1.05M |
| Max output | 128K |
| License | Proprietary |
| Open weights | No |
| Released | 2026-09 |
| Input price | $0.10 /1M |
| Output price | $0.50 /1M |
| API providers | OpenAI API |
Benchmarks
| OpenAI-reported | DeepSWE v1.1 (max) 66.6% |
|---|
What is GPT-6 Luna?
GPT-6 Luna is the cheapest and fastest model in OpenAI’s GPT-6 family, released on 22 September 2026 with GPT-6 Sol. OpenAI says that at higher effort levels it matches GPT-5.6 Sol on factuality at about a hundredth of the cost, and that at max effort it scores 66.6% on DeepSWE v1.1.
API pricing is $0.10 per million input tokens and $0.50 output (GPT-5.6 Luna: $0.20 / $1.20), with cached input at $0.01. OpenAI’s developer documentation lists a 1,050,000-token context window, up to 128,000 output tokens, text and image input, and a knowledge cutoff of 18 May 2026. Free and Go ChatGPT users can use Luna in the ChatGPT desktop app.
GPT-6 Luna pricing: API cost per 1M tokens
| Input (per 1M tokens) | $0.100 |
|---|---|
| Output (per 1M tokens) | $0.500 |
| Output/input ratio | 5× |
| Blended (4:1 in:out) | $0.180 per 1M tokens |
What GPT-6 Luna costs per month
Real monthly spend at a 4:1 input-to-output mix — the ratio a typical chat or RAG workload actually produces.
| Workload | Tokens / month | Cost / month |
|---|---|---|
| Side project | 1M in / 0.25M out | $0.23 |
| Small team | 20M in / 5M out | $4.50 |
| Production | 200M in / 50M out | $45 |
Run your own numbers in the AI API cost calculator.
Cheaper alternatives to GPT-6 Luna
| Model | Blended $/1M | You save |
|---|---|---|
| Mistral 7B open | $0.0220 | 88% cheaper |
| Llama 3.1 8B open | $0.0220 | 88% cheaper |
| Mistral NeMo 12B open | $0.0240 | 87% cheaper |
Frequently asked questions
How much does GPT-6 Luna cost per 1M tokens?
GPT-6 Luna costs $0.100 per 1M input tokens and $0.500 per 1M output tokens. At a typical 4:1 input-to-output mix that blends to about $0.180 per 1M tokens.
How much does GPT-6 Luna cost per month?
A small-team workload of 20M input and 5M output tokens a month costs about $4.50 on GPT-6 Luna. A side project (1M in / 0.25M out) costs roughly $0.23.
What is a cheaper alternative to GPT-6 Luna?
Mistral 7B is the strongest cheaper option in our database at $0.0220 per 1M blended — about 88% less than GPT-6 Luna. It is also open-weight, so self-hosting is an option.
Can I run GPT-6 Luna locally?
No. GPT-6 Luna is a closed, API-only model — the weights are not released, so it cannot be self-hosted.
Why does GPT-6 Luna charge more for output than input?
Output tokens are generated one at a time and cannot be batched the way a prompt can, so they cost the provider more to serve. GPT-6 Luna charges 5× more for output, which is why prompt-heavy workloads are far cheaper to run than generation-heavy ones.
Prices are the published list rates for the model's primary API and are reviewed as providers change them. Volume, batch and cached-input discounts are not included. Compare every model side by side in the AI models database or the LLM leaderboard.