GPT-OSS 20B vs o3

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

Quick Verdict

o3 wins overall with a score of 67 vs 22 (45 point difference).o3 wins 4 out of 4 categories.

Knowledge

o3

GPT-OSS 20B

28.8

o3

85.3

31
MMLU
86
30
GPQA
87
28
SuperGPQA
85
26
OpenBookQA
83

Coding

o3

GPT-OSS 20B

23

o3

78

23
HumanEval
78

Mathematics

o3

GPT-OSS 20B

30

o3

87

31
AIME 2023
88
33
AIME 2024
90
32
AIME 2025
89
27
HMMT Feb 2023
84
29
HMMT Feb 2024
86
28
HMMT Feb 2025
85
30
BRUMO 2025
87

Reasoning

o3

GPT-OSS 20B

28

o3

83

29
SimpleQA
84
27
MuSR
82

Frequently Asked Questions

Which is better, GPT-OSS 20B or o3?

o3 scores higher overall with 67 vs 22, a difference of 45 points across all benchmarks.

Which is better for knowledge tasks, GPT-OSS 20B or o3?

o3 leads in knowledge tasks with an average score of 85.3 vs 28.8.

Which is better for coding, GPT-OSS 20B or o3?

o3 leads in coding with an average score of 78 vs 23.

Which is better for math, GPT-OSS 20B or o3?

o3 leads in math with an average score of 87 vs 30.

Which is better for reasoning, GPT-OSS 20B or o3?

o3 leads in reasoning with an average score of 83 vs 28.