GPT-5.5 vs GPT-5.5 Pro

The match-up at a glance

GPT-5.5 and GPT-5.5 Pro are two frontier models, the ones you pick when quality comes first, both built by OpenAI. GPT-5.5 was released on April 23, 2026, GPT-5.5 Pro on April 23, 2026.

All figures below come from public sources checked on October 22, 2026: models.dev and OpenRouter for prices and capabilities, Epoch AI for scores.

What the benchmarks say

On our capability index, GPT-5.5 scores 89 out of 100 and GPT-5.5 Pro 96.9. GPT-5.5 Pro leads by 7.9 points.

On the 3 benchmarks reported for both, GPT-5.5 wins 1 time and GPT-5.5 Pro 1:

• GPQA Diamond (PhD-level science questions): GPT-5.5 94%, GPT-5.5 Pro 93.9%
• OTIS Mock AIME (competition mathematics problems): GPT-5.5 100%, GPT-5.5 Pro 100%
• FrontierMath (very hard research-level mathematics): GPT-5.5 85.3%, GPT-5.5 Pro 87.7%

Pricing

GPT-5.5 costs $5 per million input tokens and $30 per million output tokens; GPT-5.5 Pro costs $30 and $180.

For a typical agent task (read 20,000 tokens, write 2,000), expect $0.16 with GPT-5.5 versus $0.96 with GPT-5.5 Pro. GPT-5.5 is 6 times cheaper, a gap that adds up quickly over 1,000 tasks: $800 difference.

Run the numbers with your own volumes in the agent cost calculator.

Features and limits

Both models have the same context window: 1,050,000 tokens, roughly 1,575 pages.

Reasoning mode: GPT-5.5 yes, GPT-5.5 Pro yes. Tool calling: GPT-5.5 yes, GPT-5.5 Pro yes. Image input: GPT-5.5 yes, GPT-5.5 Pro yes.

Neither publishes its weights: both are used through an API.

Knowledge cutoff: December 1, 2025 for GPT-5.5, December 1, 2025 for GPT-5.5 Pro.

In short

Our reading of the data:

• Choose GPT-5.5 for a lower cost.
• Choose GPT-5.5 Pro for a higher capability index.

This verdict relies on public figures; it does not replace a trial on your own tasks.