benchlm.ai

Claude Opus 4.5 vs GPT-OSS 120B

Side-by-side benchmark comparison across knowledge, coding, math, and reasoning.

Quick Verdict

Claude Opus 4.5 wins overall with a score of 79 vs 42 (37 point difference).Claude Opus 4.5 wins 4 out of 4 categories.

Claude Opus 4.5

CreatorAnthropic
TypeProprietary
Context200K
Score79

GPT-OSS 120B

CreatorOpenAI
TypeOpen Weight
Context128K
Score42

Knowledge

Claude Opus 4.5

Claude Opus 4.5

96

GPT-OSS 120B

48.8

99
MMLU
51
97
GPQA
50
95
SuperGPQA
48
93
OpenBookQA
46

Coding

Claude Opus 4.5

Claude Opus 4.5

91

GPT-OSS 120B

43

91
HumanEval
43

Mathematics

Claude Opus 4.5

Claude Opus 4.5

97.1

GPT-OSS 120B

50

99
AIME 2023
51
99
AIME 2024
53
98
AIME 2025
52
95
HMMT Feb 2023
47
97
HMMT Feb 2024
49
96
HMMT Feb 2025
48
96
BRUMO 2025
50

Reasoning

Claude Opus 4.5

Claude Opus 4.5

94

GPT-OSS 120B

48

95
SimpleQA
49
93
MuSR
47

Frequently Asked Questions

Which is better, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 scores higher overall with 79 vs 42, a difference of 37 points across all benchmarks.

Which is better for knowledge tasks, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 leads in knowledge tasks with an average score of 96 vs 48.8.

Which is better for coding, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 leads in coding with an average score of 91 vs 43.

Which is better for math, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 leads in math with an average score of 97.1 vs 50.

Which is better for reasoning, Claude Opus 4.5 or GPT-OSS 120B?

Claude Opus 4.5 leads in reasoning with an average score of 94 vs 48.

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