GPT-5.1 Codex vs o3 Mini
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 8 of 15 benchmarks against o3 Mini by OpenAI, which leads on 6. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
General Intelligence: In general intelligence, GPT-5.1 Codex scores 1395 on Chatbot Arena ELO compared to o3 Mini's 1320, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to o3 Mini's 78.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to o3 Mini's 87.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to o3 Mini's 50.0%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to o3 Mini's 55.0%.
Math: In math, o3 Mini scores 93.0% on MATH compared to GPT-5.1 Codex's 85.0%, while o3 Mini scores 97.0% on GSM8K compared to GPT-5.1 Codex's 95.0%.
Reasoning: In reasoning, o3 Mini scores 77.0% on GPQA Diamond compared to GPT-5.1 Codex's 65.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to o3 Mini's 45.0%.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to o3 Mini's 200K.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while o3 Mini costs $1.1/1M input and $4.4/1M output. o3 Mini is the more affordable option for API usage.
Speed Comparison
GPT-5.1 Codex generates output at 85 tok/s compared to o3 Mini's 100 tok/s, and the time to first token is 400 ms for GPT-5.1 Codex versus 400 ms for o3 Mini. o3 Mini delivers faster throughput.
Verdict
For developers prioritizing coding and general intelligence, GPT-5.1 Codex has the edge. For those who value math and affordability and speed, o3 Mini is the stronger choice.
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GPT-5.1 Codex vs o3 Mini — FAQ
Which is better, GPT-5.1 Codex or o3 Mini?
GPT-5.1 Codex wins on more benchmarks overall (8 vs 6). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-5.1 Codex compare to o3 Mini for coding?
GPT-5.1 Codex is better for coding, scoring 78.0% on SWE-bench Verified compared to 50.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is GPT-5.1 Codex cheaper than o3 Mini?
Yes, o3 Mini is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. o3 Mini costs $1.1/1M input and $4.4/1M output tokens.
Which is faster, GPT-5.1 Codex or o3 Mini?
o3 Mini is faster, generating output at 100 tok/s compared to 85 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the GPT-5.1 Codex vs o3 Mini comparison cover?
This comparison covers 15 benchmarks including Chatbot Arena ELO, MMLU-Pro, HumanEval+, MATH, GPQA Diamond, SWE-bench Verified, Output Speed, LiveCodeBench, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.