Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.
Claude Opus 4.5 is clearly ahead on the aggregate, 85 to 31. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Opus 4.5's sharpest advantage is in mathematics, where it averages 96.1 against 85.2. The single biggest benchmark swing on the page is GPQA, 97 to 71.2.
GPT-5 nano is the reasoning model in the pair, while Claude Opus 4.5 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 200K for Claude Opus 4.5.
Pick Claude Opus 4.5 if you want the stronger benchmark profile. GPT-5 nano only becomes the better choice if you need the larger 400K context window or you want the stronger reasoning-first profile.
Claude Opus 4.5
80.8
GPT-5 nano
71.2
Claude Opus 4.5
96.1
GPT-5 nano
85.2
Claude Opus 4.5 is ahead overall, 85 to 31. The biggest single separator in this matchup is GPQA, where the scores are 97 and 71.2.
Claude Opus 4.5 has the edge for knowledge tasks in this comparison, averaging 80.8 versus 71.2. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Claude Opus 4.5 has the edge for math in this comparison, averaging 96.1 versus 85.2. Inside this category, AIME 2025 is the benchmark that creates the most daylight between them.
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