gpt-oss-120b vs GPT-5.5
Head-to-head specifications
| Metric | gpt-oss-120b | GPT-5.5 | Difference |
|---|---|---|---|
| Intelligence Index | 28.0 | 55.0 | -49.1% |
| Coding Index | 30.4 | 74.9 | -59.4% |
| Agentic Index | 13.2 | 44.9 | — |
| Context window | 256K tokens | 1M tokens | — |
| Blended price ($/1M tokens) | $0.20 | $1.54 | -87.0% |
| Output speed (tokens/s) | 272 | 67 | +306.0% |
| Access | Open weights | Proprietary API | — |
- GPT-5.5 leads overall capability (Intelligence Index 55.0 vs 28.0).
- gpt-oss-120b is the cheaper model to run at $0.20/1M blended tokens — about 7.7× cheaper.
- GPT-5.5 offers the larger context window (1M tokens), useful for long documents and codebases.
Verdict: gpt-oss-120b or GPT-5.5?
gpt-oss-120b advantages
- Affordability (+87%)
- Output speed (+75%)
GPT-5.5 advantages
- General intelligence (+49%)
- Coding ability (+59%)
- Agentic task performance (+71%)
- Context window (+74%)
Which should you choose?
- Choose the gpt-oss-120b if you want the lowest cost per token at scale.
- Choose the GPT-5.5 if you need the strongest overall reasoning and accuracy.
- Choose the gpt-oss-120b if low latency and fast generation matter for your application.
Value for money
gpt-oss-120b offers more intelligence per dollar (3.9× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use. It is also open-weight, so self-hosting can reduce costs further at scale.
gpt-oss-120b vs GPT-5.5: which should you choose?
gpt-oss-120b — OpenAI text model with an Intelligence Index of 28, a 256K-token context window and a blended price of $0.2/1M tokens (open weights).
GPT-5.5 — OpenAI multimodal model with an Intelligence Index of 55, a 1M-token context window and a blended price of $1.54/1M tokens.
gpt-oss-120b vs GPT-5.5: GPT-5.5 scores higher on the Intelligence Index. GPT-5.5 leads overall capability (Intelligence Index 55.0 vs 28.0). gpt-oss-120b is the cheaper model to run at $0.20/1M blended tokens — about 7.7× cheaper.
Capability: intelligence, coding and agentic work
On the composite Intelligence Index the GPT-5.5 scores 55.0 versus 28.0. For software development, the Coding Index puts GPT-5.5 ahead (74.9 vs 30.4). On agentic, multi-step tool-use tasks, GPT-5.5 measures stronger. Composite indices summarize many evaluations, but always test on your own workload before committing.
Context window and speed
The GPT-5.5 accepts up to 1 million tokens per request, which sets how much documentation, transcript or code it can reason over at once. In measured throughput, gpt-oss-120b generates faster (272 vs 67 tokens/s), which matters for interactive apps and high-volume pipelines.
Pricing and access
At blended per-token rates, gpt-oss-120b is the cheaper model to run ($0.20 vs $1.54 per 1M tokens). gpt-oss-120b is open weights and GPT-5.5 is proprietary api. Open-weight models can be self-hosted, trading per-call cost for infrastructure you manage; for production also weigh rate limits, throughput and data-residency requirements.
The verdict
Both are credible choices in the ai model comparison space; the specification table above lays out every metric so you can weigh the trade-offs that matter to you. Pick the one whose strengths line up with how you will actually use it.
Frequently asked questions
Is the gpt-oss-120b better than the GPT-5.5?
GPT-5.5 takes the overall edge, though gpt-oss-120b wins in specific areas worth weighing. GPT-5.5 leads overall capability (Intelligence Index 55.0 vs 28.0).
What is the main difference between the gpt-oss-120b and the GPT-5.5?
GPT-5.5 leads overall capability (Intelligence Index 55.0 vs 28.0). gpt-oss-120b is the cheaper model to run at $0.20/1M blended tokens — about 7.7× cheaper.
Which is better value?
gpt-oss-120b offers more intelligence per dollar (3.9× the Intelligence-Index-per-cost of the alternative), making it the stronger value for high-volume use. It is also open-weight, so self-hosting can reduce costs further at scale.
Which should I choose?
Choose the gpt-oss-120b if you want the lowest cost per token at scale. Choose the GPT-5.5 if you need the strongest overall reasoning and accuracy.
Methodology
Large language models are compared on independent leaderboard metrics: an Intelligence Index (a composite of reasoning and knowledge evaluations), Coding and Agentic indices where measured, community arena Elo, maximum context window, a blended API price per million tokens (weighted across cache-hit, input and output rates), and measured output speed in tokens per second. Where a model ships multiple reasoning-effort variants, we report its strongest variant. Benchmarks capture only part of real-world quality, which also depends on tool use, latency, safety and task fit — and this space moves quickly, so figures reflect the leaderboard snapshot on the page date.