GPT-5.5
ECI#8
159GPT-5.5 is a closed-weights model from OpenAI, released April 23, 2026. It has an ECI score of 159 and ranks 8th of 249 tracked models. At the time of its release, it ranked 2nd of 210 tracked models. At $5/Mtok for input tokens and $30/Mtok for output tokens, it is more expensive per token than similarly-capable models.
Input price$5 / 1M tokens
Output price$30 / 1M tokens
ParametersUnknown
Training computeUnknown
GPT-5.5 vs select alternatives
Reasoning
| Domain | Benchmark | GPT-5.5 | |||
|---|---|---|---|---|---|
ECI scoreBest score 166 | 159 | 159 | 156 | 155 | |
| Ranking | #8 | #9 | #18 | #27 | |
| Games | Chess PuzzlesBest score 72.0% | ||||
Earthborne Rangers (EBR-bench)Best score 76.2% | |||||
Mystery Game PuzzlesBest score 84.0% | |||||
| Mathematics | FrontierMath Tiers 1-3 (v2)Best score 93.7% | ||||
FrontierMath Tier 4 (v2)Best score 97.6% | |||||
| Science | GPQA DiamondBest score 95.8% | ||||
| Software engineering | MirrorCodeBest score 73.3% | ||||
SWE-bench VerifiedBest score 83.5% | |||||
| World knowledge | SimpleQA VerifiedBest score 75.6% |
