GPT-5.1 vs GPT-5.5 Pro
Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.
GPT-5.1
59.6OpenAI · Nov 2025
A November 2025 update to GPT-5 with adaptive reasoning that spends thinking tokens only when a task needs them.
GPT-5.5 Pro
OpenAI · Apr 2026
The maximum-compute tier of GPT-5.5 for the hardest research, math and engineering problems, at a steep per-token premium.
The verdict
These two models don't yet share verified results on the benchmarks we track, so judge them on specs, pricing and intended use. On price the gap is dramatic: GPT-5.1 works out roughly 20x cheaper per blended million tokens. GPT-5.5 Pro also takes 1M of context versus 400K for GPT-5.1.
Specs & pricing
| GPT-5.1 | GPT-5.5 Pro | |
|---|---|---|
| modhub Index | 59.6 | — |
| Input price / 1M | $1.25 | $30 |
| Output price / 1M | $10 | $180 |
| Context window | 400K | 1M |
| Max output | 128K | 128K |
| Open weights | no | no |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text, image |
| Knowledge cutoff | Sep 2024 | Jan 2026 |
| Released | Nov 2025 | Apr 2026 |
| Example monthly cost* | $27.50 | $570.00 |
* 10M input + 1.5M output tokens per month at list prices, no caching. Green = better value on that row.
Frequently asked questions
- Which is better, GPT-5.1 or GPT-5.5 Pro?
- These two models don't yet share verified results on the benchmarks we track, so judge them on specs, pricing and intended use. On price the gap is dramatic: GPT-5.1 works out roughly 20x cheaper per blended million tokens. GPT-5.5 Pro also takes 1M of context versus 400K for GPT-5.1.
- Which is cheaper, GPT-5.1 or GPT-5.5 Pro?
- GPT-5.1 costs $1.25/$10 per million input/output tokens, while GPT-5.5 Pro costs $30/$180. For a typical workload of 10M input and 1.5M output tokens per month, that's $27.50 versus $570.00.
- Which model is better for coding, GPT-5.1 or GPT-5.5 Pro?
- We don't yet track SWE-bench Verified results for both models; check their individual pages for coding-related scores.