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OpenAI · GPT
No. 08
GPT-5.5 Pro
Maximum-accuracy reasoning tier of the GPT-5.5 flagship.
Field notes
- Context window
- 1.1Mtokens
- Max output
- 128Ktokens
- Input price
- $30/ 1M tokens
- Output price
- $180/ 1M tokens
- Modalities
- Text, Image, Pdf
- Knowledge cutoff
- Dec 2025
- Released
- Apr 2026
- Approx. speed
- —
Overview
What this model is
GPT-5.5 Pro is the mandatory-reasoning, maximum-accuracy variant of OpenAI's flagship, tuned for the hardest problems where correctness outweighs cost and latency. It spends far more compute per query, pushing deeper deliberate reasoning for elite math, science, and analysis. Reserve it for the small slice of tasks that justify its steep pricing.
Strengths
- Top-tier deliberate reasoning accuracy
- Elite math and science problem solving
- Frontier coding on hard problems
- Reliable high-stakes single-shot answers
- Million-token context with multimodal input
Trade-offs
- Very expensive at $30/$180 per million tokens
- High latency from heavy reasoning
- Overkill for routine work
- No prompt-cache discount advantage at this tier
Best for
- Hardest math and science problems
- High-stakes analysis where accuracy is paramount
- Research-grade reasoning
- Complex algorithmic coding
Not ideal for
- Cost-sensitive or high-throughput workloads
- Latency-sensitive interactive apps
- Routine tasks GPT-5.5 already handles
Capabilities
Capability profile
Normalized 0–100 scores, comparable across the whole catalog.
- Reasoning
- 98
- Coding
- 95
- Math
- 97
- Writing
- 91
- Knowledge
- 95
- Speed
- 30
- Agentic
- 94
- Vision
- 89
- Multilingual
- 90
- Long Context
- 92
Benchmarks
How it scores
Public benchmark results, with independent third-party results where available. Bars normalize percentages to 100 and Elo ratings to a 1500 ceiling.
BenchmarkResult
GPQA Diamondindependent
ReasoningIndependent aggregators
94.5%
AIME 2025
MathVendor-reported
96.5%
LMArena Eloindependent
GeneralLMArena
1510Elo