Kimi K2.5 (Reasoning) vs GPT-5 nano

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

Kimi K2.5 (Reasoning) is clearly ahead on the aggregate, 82 to 31. The gap is large enough that you do not need to squint at the spreadsheet to see the difference.

Kimi K2.5 (Reasoning)'s sharpest advantage is in mathematics, where it averages 92.9 against 85.2. The single biggest benchmark swing on the page is GPQA, 90 to 71.2.

GPT-5 nano gives you the larger context window at 400K, compared with 128K for Kimi K2.5 (Reasoning).

Quick Verdict

Pick Kimi K2.5 (Reasoning) if you want the stronger benchmark profile. GPT-5 nano only becomes the better choice if you need the larger 400K context window.

Knowledge

Kimi K2.5 (Reasoning)

Kimi K2.5 (Reasoning)

77.3

GPT-5 nano

71.2

92
MMLU
-
90
GPQA
71.2
88
SuperGPQA
-
86
OpenBookQA
-
81
MMLU-Pro
-
27
HLE
-

Coding

Kimi K2.5 (Reasoning)
84
HumanEval
-
65
SWE-bench Verified
-
58
LiveCodeBench
-

Mathematics

Kimi K2.5 (Reasoning)

Kimi K2.5 (Reasoning)

92.9

GPT-5 nano

85.2

94
AIME 2023
-
96
AIME 2024
-
95
AIME 2025
85.2
90
HMMT Feb 2023
-
92
HMMT Feb 2024
-
91
HMMT Feb 2025
-
93
BRUMO 2025
-
92
MATH-500
-

Reasoning

Kimi K2.5 (Reasoning)
88
SimpleQA
-
86
MuSR
-
91
BBH
-

Instruction Following

Kimi K2.5 (Reasoning)
91
IFEval
-

Multilingual

Kimi K2.5 (Reasoning)
88
MGSM
-

Frequently Asked Questions

Which is better, Kimi K2.5 (Reasoning) or GPT-5 nano?

Kimi K2.5 (Reasoning) is ahead overall, 82 to 31. The biggest single separator in this matchup is GPQA, where the scores are 90 and 71.2.

Which is better for knowledge tasks, Kimi K2.5 (Reasoning) or GPT-5 nano?

Kimi K2.5 (Reasoning) has the edge for knowledge tasks in this comparison, averaging 77.3 versus 71.2. Inside this category, GPQA is the benchmark that creates the most daylight between them.

Which is better for math, Kimi K2.5 (Reasoning) or GPT-5 nano?

Kimi K2.5 (Reasoning) has the edge for math in this comparison, averaging 92.9 versus 85.2. Inside this category, AIME 2025 is the benchmark that creates the most daylight between them.

Last updated: March 9, 2026

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