Model Comparison

GPT-5.6 Luna vs GPT-5.5 ProWhich is better in 2026?

Both models are evenly matched across the benchmarks. GPT-5.6 Luna is 30.0x cheaper per token.

Verdict: GPT-5.6 Luna vs GPT-5.5 Pro — which is better?

GPT-5.6 Luna (by OpenAI) and GPT-5.5 Pro (by OpenAI) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

GPT-5.6 Luna outperforms in 1 benchmarks (FrontierMath), while GPT-5.5 Pro is better at 1 benchmark (BrowseComp). Both models are evenly matched across the benchmarks.

On price, GPT-5.6 Luna is roughly 30.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Choose GPT-5.6 Luna if…

  • cost matters — it's about 30.0x cheaper per token
  • you want the most recent training data — it shipped Jul 2026

Choose GPT-5.5 Pro if…

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

Performance Benchmarks

Comparative analysis across standard metrics

2 benchmarks

GPT-5.6 Luna outperforms in 1 benchmarks (FrontierMath), while GPT-5.5 Pro is better at 1 benchmark (BrowseComp).

Both models are evenly matched across the benchmarks.

Fri Jul 17 2026 • llm-stats.com

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

GPT-5.6 Luna costs less

For input processing, GPT-5.6 Luna ($1.00/1M tokens) is 30.0x cheaper than GPT-5.5 Pro ($30.00/1M tokens).

For output processing, GPT-5.6 Luna ($6.00/1M tokens) is 30.0x cheaper than GPT-5.5 Pro ($180.00/1M tokens).

In conclusion, GPT-5.5 Pro is more expensive than GPT-5.6 Luna.*

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

Lowest available price from all providers
Fri Jul 17 2026 • llm-stats.com
OpenAI
GPT-5.6 Luna
Input tokens$1.00
Output tokens$6.00
Best providerOpenAI
OpenAI
GPT-5.5 Pro
Input tokens$30.00
Output tokens$180.00
Best providerOpenAI
Notice missing or incorrect data?Start an Issue→

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-5.6 Luna
Input1,050,000 tokens
Output128,000 tokens
OpenAI
GPT-5.5 Pro
Input1,050,000 tokens
Output128,000 tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

Both GPT-5.6 Luna and GPT-5.5 Pro support multimodal inputs.

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

GPT-5.6 Luna

Text
Images
Audio
Video

GPT-5.5 Pro

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-5.6 Luna

Proprietary

Closed source

GPT-5.5 Pro

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.6 Luna was released on 2026-07-09, while GPT-5.5 Pro was released on 2026-04-23.

GPT-5.6 Luna is 3 months newer than GPT-5.5 Pro.

GPT-5.6 Luna

Jul 9, 2026

1 weeks ago

2mo newer
GPT-5.5 Pro

Apr 23, 2026

2 months ago

Knowledge Cutoff

When training data ends

GPT-5.6 Luna has a knowledge cutoff of 2026-02-16, while GPT-5.5 Pro has a cutoff of 2025-12-01.

GPT-5.6 Luna has more recent training data (up to 2026-02-16), making it potentially better informed about events through that date compared to GPT-5.5 Pro (2025-12-01).

GPT-5.6 Luna

Feb 2026

2 mo newer
GPT-5.5 Pro

Dec 2025

Provider Availability

GPT-5.6 Luna is available from OpenAI. GPT-5.5 Pro is available from OpenAI.

GPT-5.6 Luna

openai logo
OpenAI
Input Price:Input: $1.00/1MOutput Price:Output: $6.00/1M

GPT-5.5 Pro

openai logo
OpenAI
Input Price:Input: $30.00/1MOutput Price:Output: $180.00/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Less expensive input tokens
Less expensive output tokens
Higher FrontierMath score (78.6% vs 39.6%)
OpenAI
Higher BrowseComp score (90.1% vs 83.3%)

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.6 Luna and GPT-5.5 Pro side-by-side, then vote on the output you prefer.

GPT-5.6 Luna
✓ Preferred
GPT-5.5 Pro
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.6 Luna
OpenAI
GPT-5.5 Pro

FAQ

Common questions about GPT-5.6 Luna vs GPT-5.5 Pro.

Which is better, GPT-5.6 Luna or GPT-5.5 Pro?

Both models are evenly matched across the benchmarks. GPT-5.6 Luna is made by OpenAI and GPT-5.5 Pro is made by OpenAI. The best choice depends on your use case — compare their benchmark scores, pricing, and capabilities above.

How does GPT-5.6 Luna compare to GPT-5.5 Pro in benchmarks?

GPT-5.6 Luna scores Connectors: 99.9%, HealthBench Consensus: 95.1%, GPQA: 92.3%, Search and Function-Calling: 89.7%, Capture-the-Flag Challenges (Internal): 85.2%. GPT-5.5 Pro scores BrowseComp: 90.1%, GDPval-MM: 82.3%, Humanity's Last Exam: 57.2%, FrontierMath: 39.6%, GeneBench: 33.2%.

Is GPT-5.6 Luna cheaper than GPT-5.5 Pro?

GPT-5.6 Luna is 30.0x cheaper for input tokens. GPT-5.6 Luna costs $1.00/M input and $6.00/M output via openai. GPT-5.5 Pro costs $30.00/M input and $180.00/M output via openai.

What are the context window sizes for GPT-5.6 Luna and GPT-5.5 Pro?

GPT-5.6 Luna supports 1.1M tokens and GPT-5.5 Pro 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-5.6 Luna and GPT-5.5 Pro?

Key differences include input pricing ($1.00 vs $30.00/M). See the full comparison above for benchmark-by-benchmark results.

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