GPT-5.5 Pro
ECI#5
162GPT-5.5 Pro is a closed-weights model from OpenAI, released April 23, 2026. It has an ECI score of 162 and ranks 5th of 249 tracked models. At the time of its release, it ranked 1st of 210 tracked models. At $30/Mtok for input tokens and $180/Mtok for output tokens, it is more expensive per token than similarly-capable models.
Input price$30 / 1M tokens
Output price$180 / 1M tokens
ParametersUnknown
Training computeUnknown
GPT-5.5 Pro vs select alternatives
Reasoning
| Domain | Benchmark | GPT-5.5 Pro | |||
|---|---|---|---|---|---|
ECI scoreBest score 166 | 162 | 159 | 156 | 155 | |
| Ranking | #5 | #9 | #18 | #27 | |
| Conceptual reasoning | SimpleBenchBest score 81.9% | ||||
ARC-AGI-2Best score 95.0% | |||||
ARC-AGI-1Best score 98.5% | |||||
| Games | Chess PuzzlesBest score 72.0% | ||||
| Mathematics | FrontierMath Tiers 1-3 (v2)Best score 93.7% | ||||
FrontierMath Tier 4 (v2)Best score 97.6% | |||||
OTIS Mock AIME 2024-2025Best score 100.0% | |||||
| Science | CritPtBest score 32.3% | ||||
GPQA DiamondBest score 95.8% |
