GPT OSS 120B vs GPT OSS 20B: Specs & Benchmark Comparison
GPT OSS 120B and GPT OSS 20B both come from OpenAI, and both were released in August 2025. GPT OSS 120B is the larger model at roughly 120 billion parameters, against 20 billion for GPT OSS 20B.
The two models share 9 published benchmarks. GPT OSS 120B leads on 8 of them, GPT OSS 20B on 1. The widest gaps are on Codeforces Competition code, where GPT OSS 20B scores 74.3% against 26.2%; HealthBench Hard - Challenging health conversations, where GPT OSS 120B scores 30.0% against 10.8%. Averaged across everything we track, GPT OSS 120B sits at 52.0% and GPT OSS 20B at 43.6%.
GPT OSS 20B is the cheaper API at $0.10 per million input tokens and $0.50 per million output tokens, about 50% below GPT OSS 120B at $0.15 and $0.60. Both accept a context window of about 131K tokens.
| Characteristic | GPT OSS 120B | GPT OSS 20B |
|---|---|---|
| Company | OpenAI | OpenAI |
| Release Date | August 5, 2025 | August 5, 2025 |
| Parameters | 120B | 20B |
| Multimodal | Yes | Yes |
| Context (input) | 131K | 131K |
| Context (output) | 30K | 30K |
| Input Price / 1M | $0.15 | $0.10 |
| Output Price / 1M | $0.60 | $0.50 |
| Average Score | 52.0% | 43.6% |
| Benchmarks | ||
| Codeforces Competition code | 26.2% | 74.3% |
| HealthBench Hard - Challenging health conversations | 30.0% | 10.8% |
| HealthBench - Realistic health conversations | 57.6% | 42.5% |
| TAU-bench Retail benchmark | 67.8% | 54.8% |
| GPQA | 80.1% | 71.5% |
| Humanity's Last Exam | 19.0% | 10.9% |
| Codeforces Competition code | 82.1% | 74.3% |
| MMLU benchmark | 90.0% | 85.3% |
| Humanity's Last Exam | 14.9% | 10.9% |
Visual Benchmark Comparison
Verdict
GPT OSS 20B leads in 1 out of 4 comparison categories.
Both models show comparable average scores: GPT OSS 120B — 0.5, GPT OSS 20B — 0.4.
GPT OSS 20B is 1.3x cheaper: input $0.10/1M vs $0.15/1M tokens.
Same context size: 131K tokens.
Both models were released around the same time: 8/5/2025 and 8/5/2025.
More About These Models
Frequently Asked Questions
Which is better for coding — GPT OSS 120B or GPT OSS 20B?
Which model is cheaper — GPT OSS 120B or GPT OSS 20B?
Which has a larger context window — GPT OSS 120B or GPT OSS 20B?
The GPT OSS 120B and GPT OSS 20B comparison is updated for 2026. Data includes benchmark results, API pricing, context window size and other specifications. For more detailed information, visit the GPT OSS 120B or GPT OSS 20B page. See also the complete list of AI model comparisons.