benchlm.ai

GPT-5 (medium) vs GPT-OSS 20B

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

Quick Verdict

GPT-5 (medium) wins overall with a score of 70 vs 22 (48 point difference).GPT-5 (medium) wins 4 out of 4 categories.

GPT-5 (medium)

CreatorOpenAI
TypeProprietary
Context128K
Score70

GPT-OSS 20B

CreatorOpenAI
TypeOpen Weight
Context128K
Score22

Knowledge

GPT-5 (medium)

GPT-5 (medium)

88

GPT-OSS 20B

28.8

91
MMLU
31
89
GPQA
30
87
SuperGPQA
28
85
OpenBookQA
26

Coding

GPT-5 (medium)

GPT-5 (medium)

83

GPT-OSS 20B

23

83
HumanEval
23

Mathematics

GPT-5 (medium)

GPT-5 (medium)

92

GPT-OSS 20B

30

93
AIME 2023
31
95
AIME 2024
33
94
AIME 2025
32
89
HMMT Feb 2023
27
91
HMMT Feb 2024
29
90
HMMT Feb 2025
28
92
BRUMO 2025
30

Reasoning

GPT-5 (medium)

GPT-5 (medium)

86

GPT-OSS 20B

28

87
SimpleQA
29
85
MuSR
27

Frequently Asked Questions

Which is better, GPT-5 (medium) or GPT-OSS 20B?

GPT-5 (medium) scores higher overall with 70 vs 22, a difference of 48 points across all benchmarks.

Which is better for knowledge tasks, GPT-5 (medium) or GPT-OSS 20B?

GPT-5 (medium) leads in knowledge tasks with an average score of 88 vs 28.8.

Which is better for coding, GPT-5 (medium) or GPT-OSS 20B?

GPT-5 (medium) leads in coding with an average score of 83 vs 23.

Which is better for math, GPT-5 (medium) or GPT-OSS 20B?

GPT-5 (medium) leads in math with an average score of 92 vs 30.

Which is better for reasoning, GPT-5 (medium) or GPT-OSS 20B?

GPT-5 (medium) leads in reasoning with an average score of 86 vs 28.

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