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GPT-5.5 Pro vs GPT-6 Luna

GPT-5.5 Pro and GPT-6 Luna are closely matched at 45.9 and 43.1 on the LLM Stats Score. GPT-6 Luna is 337.5x cheaper per token.

OpenAI · OpenAI · Updated for 2026

Which is better?

GPT-5.5 Pro and GPT-6 Luna are closely matched on the overall LLM Stats Score at 45.9 and 43.1.

On price, GPT-6 Luna is roughly 337.5x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.

Choose GPT-5.5 Pro

  • you want predictable pricing at $30.00/M input and $180.00/M output

Choose GPT-6 Luna

  • cost matters — it's about 337.5x cheaper per token
  • you want the most recent training data — it shipped Sep 2026

At a glance

The differences that matter most.

GPT-5.5 Pro
OpenAI
GPT-6 Luna
OpenAI
Core performance indexes
LLM Stats Score
45.9
#38
43.1
#55
Reasoning
45.9
#34
39.9
#69
Agents
31.1
#41
30.1
#47
Cost, coverage & limits
Benchmark wins
—
—
Input price
$30.00 / M
$0.10 / M
Output price
$180.00 / M
$0.50 / M
Context window
1,050,000
1,050,000

Individual benchmarks

5 reported for GPT-5.5 Pro · 5 for GPT-6 Luna

No common benchmarks found

GPT-5.5 Pro 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

GPT-6 Luna costs less

For input processing, GPT-5.5 Pro ($30.00/1M tokens) is 300.0x more expensive than GPT-6 Luna ($0.10/1M tokens).

For output processing, GPT-5.5 Pro ($180.00/1M tokens) is 360.0x more expensive than GPT-6 Luna ($0.50/1M tokens).

In conclusion, GPT-5.5 Pro is more expensive than GPT-6 Luna.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Oct 23 2026 • llm-stats.com
OpenAI
GPT-5.5 Pro
Input tokens$30.00
Output tokens$180.00
Best providerOpenAI
OpenAI
GPT-6 Luna
Input tokens$0.10
Output tokens$0.50
Best providerOpenAI
Notice missing or incorrect data?

Context Window

Maximum input and output token capacity

Both models have the same input context window of 1,050,000 tokens. Both models can generate responses up to 128,000 tokens.

OpenAI
GPT-5.5 Pro
Input1,050,000 tokens
Output128,000 tokens
OpenAI
GPT-6 Luna
Input1,050,000 tokens
Output128,000 tokens
Fri Oct 23 2026 • llm-stats.com

Input capabilities

Documented input modalities across available providers

Both GPT-5.5 Pro and GPT-6 Luna support multimodal inputs.

They are both capable of processing various types of data, offering versatility in application.

GPT-5.5 Pro

Text
Images
Audio
Video

GPT-6 Luna

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

GPT-5.5 Pro

Proprietary

Closed source

GPT-6 Luna

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.5 Pro was released on 2026-04-23, while GPT-6 Luna was released on 2026-09-22.

GPT-6 Luna is 5 months newer than GPT-5.5 Pro.

GPT-5.5 Pro

Apr 23, 2026

5 months ago

GPT-6 Luna

Sep 22, 2026

3 weeks ago

5mo newer

Knowledge Cutoff

When training data ends

GPT-5.5 Pro has a knowledge cutoff of 2025-12-01, while GPT-6 Luna has a cutoff of 2026-05-18.

GPT-6 Luna has more recent training data (up to 2026-05-18), making it potentially better informed about events through that date compared to GPT-5.5 Pro (2025-12-01).

GPT-5.5 Pro

Dec 2025

GPT-6 Luna

May 2026

5 mo newer

Provider Availability

GPT-5.5 Pro is available from OpenAI. GPT-6 Luna is available from OpenAI.

GPT-5.5 Pro

openai logo
OpenAI
Input Price:Input: $30.00/1MOutput Price:Output: $180.00/1M

GPT-6 Luna

openai logo
OpenAI
Input Price:Input: $0.10/1MOutput Price:Output: $0.50/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?

Judge for yourself.

Run your own prompts against GPT-5.5 Pro and GPT-6 Luna side-by-side, then vote on the output you prefer.

GPT-5.5 Pro
✓ Preferred
GPT-6 Luna
Open in Playground

FAQ

Common questions about GPT-5.5 Pro vs GPT-6 Luna.

Which is better, GPT-5.5 Pro or GPT-6 Luna?

GPT-5.5 Pro and GPT-6 Luna are closely matched on the LLM Stats Score at 45.9 and 43.1. GPT-5.5 Pro is made by OpenAI and GPT-6 Luna is made by OpenAI. The best choice depends on your use case — compare their capability indexes, individual benchmarks, pricing, and limits above.

How does GPT-5.5 Pro compare to GPT-6 Luna in benchmarks?

GPT-5.5 Pro scores BrowseComp: 90.1%, GDPval-MM: 82.3%, Humanity's Last Exam: 57.2%, FrontierMath: 39.6%, GeneBench: 33.2%. GPT-6 Luna scores DeepSWE 1.1: 66.6%, OSWorld 2.0: 52.7%, Agents' Last Exam: 50.9%, FrontierCode 1.1: 42.4%, AutomationBench v1.0.6: 20.7%.

Is GPT-5.5 Pro cheaper than GPT-6 Luna?

GPT-6 Luna is 300.0x cheaper for input tokens. GPT-5.5 Pro costs $30.00/M input and $180.00/M output via openai. GPT-6 Luna costs $0.10/M input and $0.50/M output via openai.

What are the context window sizes for GPT-5.5 Pro and GPT-6 Luna?

GPT-5.5 Pro supports 1.1M tokens and GPT-6 Luna supports 1.1M tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.5 Pro and GPT-6 Luna?

Key differences include LLM Stats Score (45.9 vs 43.1), input pricing ($30.00 vs $0.10/M). See the full comparison above for benchmark-by-benchmark results.

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