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

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

Quick Verdict

GPT-5 (high) wins overall with a score of 72 vs 22 (50 point difference).GPT-5 (high) wins 4 out of 4 categories.

Knowledge

GPT-5 (high)

GPT-5 (high)

90

GPT-OSS 20B

28.8

93
MMLU
31
91
GPQA
30
89
SuperGPQA
28
87
OpenBookQA
26

Coding

GPT-5 (high)

GPT-5 (high)

85

GPT-OSS 20B

23

85
HumanEval
23

Mathematics

GPT-5 (high)

GPT-5 (high)

94

GPT-OSS 20B

30

95
AIME 2023
31
97
AIME 2024
33
96
AIME 2025
32
91
HMMT Feb 2023
27
93
HMMT Feb 2024
29
92
HMMT Feb 2025
28
94
BRUMO 2025
30

Reasoning

GPT-5 (high)

GPT-5 (high)

88

GPT-OSS 20B

28

89
SimpleQA
29
87
MuSR
27

Frequently Asked Questions

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

GPT-5 (high) scores higher overall with 72 vs 22, a difference of 50 points across all benchmarks.

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

GPT-5 (high) leads in knowledge tasks with an average score of 90 vs 28.8.

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

GPT-5 (high) leads in coding with an average score of 85 vs 23.

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

GPT-5 (high) leads in math with an average score of 94 vs 30.

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

GPT-5 (high) leads in reasoning with an average score of 88 vs 28.