benchlm.ai

Claude Sonnet 4.5 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 74 (11 point difference).GPT-5.3 Codex wins 4 out of 4 categories.

Claude Sonnet 4.5

CreatorAnthropic
TypeProprietary
Context1M
Score74

GPT-5.3 Codex

CreatorOpenAI
TypeProprietary
Context400K
Score85

Knowledge

GPT-5.3 Codex

Claude Sonnet 4.5

92

GPT-5.3 Codex

96

95
MMLU
99
93
GPQA
97
91
SuperGPQA
95
89
OpenBookQA
93

Coding

GPT-5.3 Codex

Claude Sonnet 4.5

87

GPT-5.3 Codex

95

87
HumanEval
95

Mathematics

GPT-5.3 Codex

Claude Sonnet 4.5

96

GPT-5.3 Codex

97.1

97
AIME 2023
99
99
AIME 2024
99
98
AIME 2025
98
93
HMMT Feb 2023
95
95
HMMT Feb 2024
97
94
HMMT Feb 2025
96
96
BRUMO 2025
96

Reasoning

GPT-5.3 Codex

Claude Sonnet 4.5

90

GPT-5.3 Codex

94

91
SimpleQA
95
89
MuSR
93

Frequently Asked Questions

Which is better, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex scores higher overall with 85 vs 74, a difference of 11 points across all benchmarks.

Which is better for knowledge tasks, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex leads in knowledge tasks with an average score of 96 vs 92.

Which is better for coding, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex leads in coding with an average score of 95 vs 87.

Which is better for math, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex leads in math with an average score of 97.1 vs 96.

Which is better for reasoning, Claude Sonnet 4.5 or GPT-5.3 Codex?

GPT-5.3 Codex leads in reasoning with an average score of 94 vs 90.

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