benchlm.ai

GPT-5.1-Codex-Max vs GPT-OSS 120B

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

Quick Verdict

GPT-5.1-Codex-Max wins overall with a score of 77 vs 42 (35 point difference).GPT-5.1-Codex-Max wins 4 out of 4 categories.

GPT-5.1-Codex-Max

CreatorOpenAI
TypeProprietary
Context400K
Score77

GPT-OSS 120B

CreatorOpenAI
TypeOpen Weight
Context128K
Score42

Knowledge

GPT-5.1-Codex-Max

GPT-5.1-Codex-Max

95

GPT-OSS 120B

48.8

98
MMLU
51
96
GPQA
50
94
SuperGPQA
48
92
OpenBookQA
46

Coding

GPT-5.1-Codex-Max

GPT-5.1-Codex-Max

94

GPT-OSS 120B

43

94
HumanEval
43

Mathematics

GPT-5.1-Codex-Max

GPT-5.1-Codex-Max

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

GPT-5.1-Codex-Max

GPT-5.1-Codex-Max

93

GPT-OSS 120B

48

94
SimpleQA
49
92
MuSR
47

Frequently Asked Questions

Which is better, GPT-5.1-Codex-Max or GPT-OSS 120B?

GPT-5.1-Codex-Max scores higher overall with 77 vs 42, a difference of 35 points across all benchmarks.

Which is better for knowledge tasks, GPT-5.1-Codex-Max or GPT-OSS 120B?

GPT-5.1-Codex-Max leads in knowledge tasks with an average score of 95 vs 48.8.

Which is better for coding, GPT-5.1-Codex-Max or GPT-OSS 120B?

GPT-5.1-Codex-Max leads in coding with an average score of 94 vs 43.

Which is better for math, GPT-5.1-Codex-Max or GPT-OSS 120B?

GPT-5.1-Codex-Max leads in math with an average score of 97.1 vs 50.

Which is better for reasoning, GPT-5.1-Codex-Max or GPT-OSS 120B?

GPT-5.1-Codex-Max leads in reasoning with an average score of 93 vs 48.

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