GPT-4o vs GPT-5.1 Codex
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 13 of 15 benchmarks against GPT-4o by OpenAI, which leads on 1. 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 GPT-4o's 1280, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to GPT-4o's 72.6%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to GPT-4o's 87.2%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to GPT-4o's 30.7%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to GPT-4o's 38.0%.
Math: In math, GPT-5.1 Codex scores 85.0% on MATH compared to GPT-4o's 74.6%, while GPT-5.1 Codex scores 95.0% on GSM8K compared to GPT-4o's 92.0%.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to GPT-4o's 53.6%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to GPT-4o's 5.0%.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to GPT-4o's 128K.
Pricing Comparison
GPT-4o costs $2.5/1M input tokens and $10.0/1M output tokens, while GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output. GPT-5.1 Codex is the more affordable option for API usage.
Speed Comparison
GPT-4o generates output at 143 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 450 ms for GPT-4o versus 400 ms for GPT-5.1 Codex. GPT-4o delivers faster throughput.
Verdict
For developers prioritizing speed, GPT-4o has the edge. For those who value coding and general intelligence and math and affordability, GPT-5.1 Codex is the stronger choice.
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GPT-4o vs GPT-5.1 Codex — FAQ
Which is better, GPT-4o or GPT-5.1 Codex?
GPT-5.1 Codex wins on more benchmarks overall (13 vs 1). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-4o compare to GPT-5.1 Codex for coding?
GPT-5.1 Codex is better for coding, scoring 78.0% on SWE-bench Verified compared to 30.7%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is GPT-4o cheaper than GPT-5.1 Codex?
Yes, GPT-5.1 Codex is cheaper. GPT-4o costs $2.5/1M input and $10.0/1M output tokens. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens.
Which is faster, GPT-4o or GPT-5.1 Codex?
GPT-4o is faster, generating output at 143 tok/s compared to 85 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the GPT-4o vs GPT-5.1 Codex 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.