GPT-5.1 Medium vs GPT-6 Luna
GPT-5.1 Medium and GPT-6 Luna are closely matched at 30.9 and 43.1 on the LLM Stats Score. GPT-6 Luna is 17.2x cheaper per token.
OpenAI · OpenAI · Updated for 2026
Which is better?
GPT-5.1 Medium and GPT-6 Luna are closely matched on the overall LLM Stats Score at 30.9 and 43.1.
On price, GPT-6 Luna is roughly 17.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-6 Luna also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose GPT-5.1 Medium
- you want predictable pricing at $1.25/M input and $10.00/M output
Choose GPT-6 Luna
- cost matters — it's about 17.2x cheaper per token
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Sep 2026
At a glance
The differences that matter most.
Individual benchmarks
1 reported for GPT-5.1 Medium · 5 for GPT-6 Luna
GPT-5.1 Medium and GPT-6 Lunadon't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GPT-5.1 Medium ($1.25/1M tokens) is 12.5x more expensive than GPT-6 Luna ($0.10/1M tokens).
For output processing, GPT-5.1 Medium ($10.00/1M tokens) is 20.0x more expensive than GPT-6 Luna ($0.50/1M tokens).
In conclusion, GPT-5.1 Medium is more expensive than GPT-6 Luna.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-6 Luna accepts 1,050,000 input tokens compared to GPT-5.1 Medium's 400,000 tokens. Both models can generate responses up to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
Both GPT-5.1 Medium and GPT-6 Luna support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GPT-5.1 Medium
GPT-6 Luna
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
GPT-5.1 Medium was released on 2025-11-12, while GPT-6 Luna was released on 2026-09-22.
GPT-6 Luna is 10 months newer than GPT-5.1 Medium.
Nov 12, 2025
11 months ago
Sep 22, 2026
1 months ago
10mo newerKnowledge Cutoff
When training data ends
GPT-6 Luna has a documented knowledge cutoff of 2026-05-18, while GPT-5.1 Medium's cutoff date is not specified.
We can confirm GPT-6 Luna's training data extends to 2026-05-18, but cannot make a direct comparison without GPT-5.1 Medium's cutoff date.
—
May 2026
Provider Availability
GPT-5.1 Medium is available from OpenAI. GPT-6 Luna is available from OpenAI.
GPT-5.1 Medium
GPT-6 Luna
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.1 Medium and GPT-6 Luna side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.1 Medium vs GPT-6 Luna.