Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.
Claude Sonnet 4.5 is clearly ahead on the aggregate, 83 to 31. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.
Claude Sonnet 4.5's sharpest advantage is in mathematics, where it averages 95 against 85.2. The single biggest benchmark swing on the page is GPQA, 93 to 71.2.
Claude Sonnet 4.5 is also the more expensive model on tokens at $3.00 input / $15.00 output per 1M tokens, versus $0.05 input / $0.40 output per 1M tokens for GPT-5 nano. That is roughly 37.5x on output cost alone. GPT-5 nano is the reasoning model in the pair, while Claude Sonnet 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 Sonnet 4.5.
Pick Claude Sonnet 4.5 if you want the stronger benchmark profile. GPT-5 nano only becomes the better choice if you want the cheaper token bill or you need the larger 400K context window.
Claude Sonnet 4.5
78.8
GPT-5 nano
71.2
Claude Sonnet 4.5
95
GPT-5 nano
85.2
Claude Sonnet 4.5 is ahead overall, 83 to 31. The biggest single separator in this matchup is GPQA, where the scores are 93 and 71.2.
Claude Sonnet 4.5 has the edge for knowledge tasks in this comparison, averaging 78.8 versus 71.2. Inside this category, GPQA is the benchmark that creates the most daylight between them.
Claude Sonnet 4.5 has the edge for math in this comparison, averaging 95 versus 85.2. Inside this category, AIME 2025 is the benchmark that creates the most daylight between them.
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