Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.
GPT-OSS 120B is clearly ahead on the aggregate, 50 to 31. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
GPT-5 nano is the reasoning model in the pair, while GPT-OSS 120B is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. GPT-5 nano gives you the larger context window at 400K, compared with 128K for GPT-OSS 120B.
Pick GPT-OSS 120B if you want the stronger benchmark profile. GPT-5 nano only becomes the better choice if mathematics is the priority or you need the larger 400K context window.
GPT-OSS 120B
43.8
GPT-5 nano
71.2
GPT-OSS 120B
52.6
GPT-5 nano
85.2
GPT-OSS 120B is ahead overall, 50 to 31. The biggest single separator in this matchup is AIME 2025, where the scores are 52 and 85.2.
GPT-5 nano has the edge for knowledge tasks in this comparison, averaging 71.2 versus 43.8. Inside this category, GPQA is the benchmark that creates the most daylight between them.
GPT-5 nano has the edge for math in this comparison, averaging 85.2 versus 52.6. Inside this category, AIME 2025 is the benchmark that creates the most daylight between them.
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