GPT-5.5 Pro vs gpt-oss-120b
Benchmarks, API pricing and specs, head to head. Data updated 2026-06-10.
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.
OpenAI · Aug 2025
OpenAI's open-weights MoE reasoning model under Apache 2.0 — near o4-mini quality, runnable on a single 80GB GPU.
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-oss-120b works out roughly 338x cheaper per blended million tokens. GPT-5.5 Pro also takes 1M of context versus 131K for gpt-oss-120b. And gpt-oss-120b is open-weights (Apache 2.0), so it can be self-hosted — a structural advantage if data control or vendor independence matters.
Specs & pricing
| GPT-5.5 Pro | gpt-oss-120b | |
|---|---|---|
| modhub Index | — | — |
| Input price / 1M | $30 | $0.1 |
| Output price / 1M | $180 | $0.5 |
| Context window | 1M | 131K |
| Max output | 128K | 131K |
| Open weights | no | yes (Apache 2.0) |
| Reasoning model | yes | yes |
| Multimodal input | text, image | text |
| Knowledge cutoff | Jan 2026 | Jun 2024 |
| Released | Apr 2026 | Aug 2025 |
| Example monthly cost* | $570.00 | $1.75 |
* 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-5.5 Pro or gpt-oss-120b?
- 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-oss-120b works out roughly 338x cheaper per blended million tokens. GPT-5.5 Pro also takes 1M of context versus 131K for gpt-oss-120b. And gpt-oss-120b is open-weights (Apache 2.0), so it can be self-hosted — a structural advantage if data control or vendor independence matters.
- Which is cheaper, GPT-5.5 Pro or gpt-oss-120b?
- GPT-5.5 Pro costs $30/$180 per million input/output tokens, while gpt-oss-120b costs $0.1/$0.5. For a typical workload of 10M input and 1.5M output tokens per month, that's $570.00 versus $1.75.
- Which model is better for coding, GPT-5.5 Pro or gpt-oss-120b?
- We don't yet track SWE-bench Verified results for both models; check their individual pages for coding-related scores.