benchlm.ai

Claude 3.5 Sonnet vs GPT-5.3 Codex

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

Quick Verdict

GPT-5.3 Codex wins overall with a score of 85 vs 55 (30 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

Claude 3.5 Sonnet

CreatorAnthropic
TypeProprietary
Context200K
Score55

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Knowledge

GPT-5.3 Codex

Claude 3.5 Sonnet

63.5

GPT-5.3 Codex

96

65
MMLU
99
65
GPQA
97
63
SuperGPQA
95
61
OpenBookQA
93

Coding

GPT-5.3 Codex

Claude 3.5 Sonnet

57

GPT-5.3 Codex

95

57
HumanEval
95

Mathematics

GPT-5.3 Codex

Claude 3.5 Sonnet

64

GPT-5.3 Codex

97.1

65
AIME 2023
99
67
AIME 2024
99
66
AIME 2025
98
61
HMMT Feb 2023
95
63
HMMT Feb 2024
97
62
HMMT Feb 2025
96
64
BRUMO 2025
96

Reasoning

GPT-5.3 Codex

Claude 3.5 Sonnet

62

GPT-5.3 Codex

94

63
SimpleQA
95
61
MuSR
93

Frequently Asked Questions

Which is better, Claude 3.5 Sonnet or GPT-5.3 Codex?

GPT-5.3 Codex scores higher overall with 85 vs 55, a difference of 30 points across all benchmarks.

Which is better for knowledge tasks, Claude 3.5 Sonnet or GPT-5.3 Codex?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 63.5.

Which is better for coding, Claude 3.5 Sonnet or GPT-5.3 Codex?

GPT-5.3 Codex leads in coding with an average score of 95 vs 57.

Which is better for math, Claude 3.5 Sonnet or GPT-5.3 Codex?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 64.

Which is better for reasoning, Claude 3.5 Sonnet or GPT-5.3 Codex?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 62.

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