Llama 3.1 405B vs o3-mini

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

Llama 3.1 405B is clearly ahead on the aggregate, 65 to 56. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

o3-mini is the reasoning model in the pair, while Llama 3.1 405B is not. That usually helps on harder chain-of-thought-heavy tests, but it can also mean more latency and more token spend in real use. o3-mini gives you the larger context window at 200K, compared with 128K for Llama 3.1 405B.

Quick Verdict

Pick Llama 3.1 405B if you want the stronger benchmark profile. o3-mini only becomes the better choice if knowledge is the priority or you need the larger 200K context window.

Knowledge

o3-mini

Llama 3.1 405B

58.7

o3-mini

82.1

70
MMLU
86.9
70
GPQA
77.2
68
SuperGPQA
-
66
OpenBookQA
-
71
MMLU-Pro
-
7
HLE
-

Coding

o3-mini

Llama 3.1 405B

48.3

o3-mini

49.3

62
HumanEval
-
46
SWE-bench Verified
49.3
37
LiveCodeBench
-

Mathematics

o3-mini

Llama 3.1 405B

70.6

o3-mini

87.3

70
AIME 2023
-
72
AIME 2024
87.3
71
AIME 2025
-
66
HMMT Feb 2023
-
68
HMMT Feb 2024
-
67
HMMT Feb 2025
-
69
BRUMO 2025
-
82
MATH-500
-

Reasoning

Llama 3.1 405B
68
SimpleQA
-
66
MuSR
-
82
BBH
-

Instruction Following

o3-mini

Llama 3.1 405B

86

o3-mini

93.9

86
IFEval
93.9

Multilingual

Llama 3.1 405B
84
MGSM
-

Frequently Asked Questions

Which is better, Llama 3.1 405B or o3-mini?

Llama 3.1 405B is ahead overall, 65 to 56. The biggest single separator in this matchup is MMLU, where the scores are 70 and 86.9.

Which is better for knowledge tasks, Llama 3.1 405B or o3-mini?

o3-mini has the edge for knowledge tasks in this comparison, averaging 82.1 versus 58.7. Inside this category, MMLU is the benchmark that creates the most daylight between them.

Which is better for coding, Llama 3.1 405B or o3-mini?

o3-mini has the edge for coding in this comparison, averaging 49.3 versus 48.3. Inside this category, SWE-bench Verified is the benchmark that creates the most daylight between them.

Which is better for math, Llama 3.1 405B or o3-mini?

o3-mini has the edge for math in this comparison, averaging 87.3 versus 70.6. Inside this category, AIME 2024 is the benchmark that creates the most daylight between them.

Which is better for instruction following, Llama 3.1 405B or o3-mini?

o3-mini has the edge for instruction following in this comparison, averaging 93.9 versus 86. Inside this category, IFEval is the benchmark that creates the most daylight between them.

Last updated: March 9, 2026

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