GPT-5.5 Pro vs Mercury 3
GPT-5.5 Pro leads the LLM Stats Score 45.9 to 36.1. Mercury 3 is 415.4x cheaper per token.
OpenAI · Inception · Updated for 2026
Which is better?
GPT-5.5 Pro leads the overall LLM Stats Score 45.9 to 36.1, ranking #38 overall.
On price, Mercury 3 is roughly 415.4x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.5 Pro 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-5.5 Pro
- overall performance matters — it scores 45.9 and ranks #38 on LLM Stats
- your work emphasizes reasoning and agents — it leads those capability indexes
- you process long inputs — it offers a 1,050,000 token context window
Choose Mercury 3
- cost matters — it's about 415.4x cheaper per token
- you want the most recent training data — it shipped Oct 2026
At a glance
The differences that matter most.
Individual benchmarks
5 reported for GPT-5.5 Pro · 12 for Mercury 3
GPT-5.5 Pro and Mercury 3don'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-5.5 Pro ($30.00/1M tokens) is 300.0x more expensive than Mercury 3 ($0.10/1M tokens).
For output processing, GPT-5.5 Pro ($180.00/1M tokens) is 514.3x more expensive than Mercury 3 ($0.35/1M tokens).
In conclusion, GPT-5.5 Pro is more expensive than Mercury 3.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.5 Pro accepts 1,050,000 input tokens compared to Mercury 3's 1,000,000 tokens. Mercury 3 can generate longer responses up to 131,072 tokens, while GPT-5.5 Pro is limited to 128,000 tokens.
Input capabilities
Documented input modalities across available providers
GPT-5.5 Pro supports multimodal inputs, whereas Mercury 3 does not.
GPT-5.5 Pro can handle both text and other forms of data like images, making it suitable for multimodal applications.
GPT-5.5 Pro
Mercury 3
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-5.5 Pro was released on 2026-04-23, while Mercury 3 was released on 2026-10-19.
Mercury 3 is 6 months newer than GPT-5.5 Pro.
Apr 23, 2026
5 months ago
Oct 19, 2026
0 days ago
5mo newerKnowledge Cutoff
When training data ends
GPT-5.5 Pro has a documented knowledge cutoff of 2025-12-01, while Mercury 3's cutoff date is not specified.
We can confirm GPT-5.5 Pro's training data extends to 2025-12-01, but cannot make a direct comparison without Mercury 3's cutoff date.
Dec 2025
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Provider Availability
GPT-5.5 Pro is available from OpenAI. Mercury 3 is available from Inception.
GPT-5.5 Pro
Mercury 3
Outputs Comparison
Judge for yourself.
Run your own prompts against GPT-5.5 Pro and Mercury 3 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GPT-5.5 Pro vs Mercury 3.