GPT-5.1 Codex vs GPT-5 Nano
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 9 of 15 benchmarks against GPT-5 Nano by OpenAI, which leads on 5. 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-5 Nano's 1200, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to GPT-5 Nano's 62.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to GPT-5 Nano's 72.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to GPT-5 Nano's 25.0%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to GPT-5 Nano's 30.0%.
Math: In math, GPT-5.1 Codex scores 85.0% on MATH compared to GPT-5 Nano's 65.0%, while GPT-5.1 Codex scores 95.0% on GSM8K compared to GPT-5 Nano's 85.0%.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to GPT-5 Nano's 35.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to GPT-5 Nano's 15.0%.
Context: In context, both score 400K on Context Length.
Pricing Comparison
GPT-5.1 Codex costs $1.3/1M input tokens and $10.0/1M output tokens, while GPT-5 Nano costs $0.05/1M input and $0.40/1M output. GPT-5 Nano is the more affordable option for API usage.
Speed Comparison
GPT-5.1 Codex generates output at 85 tok/s compared to GPT-5 Nano's 250 tok/s, and the time to first token is 400 ms for GPT-5.1 Codex versus 80 ms for GPT-5 Nano. GPT-5 Nano delivers faster throughput.
Verdict
For developers prioritizing coding and general intelligence and math, GPT-5.1 Codex has the edge. For those who value affordability and speed, GPT-5 Nano is the stronger choice.
View Individual Model Pages
GPT-5.1 Codex vs GPT-5 Nano — FAQ
Which is better, GPT-5.1 Codex or GPT-5 Nano?
GPT-5.1 Codex wins on more benchmarks overall (9 vs 5). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-5.1 Codex compare to GPT-5 Nano for coding?
GPT-5.1 Codex is better for coding, scoring 78.0% on SWE-bench Verified compared to 25.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is GPT-5.1 Codex cheaper than GPT-5 Nano?
Yes, GPT-5 Nano is cheaper. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens. GPT-5 Nano costs $0.05/1M input and $0.40/1M output tokens.
Which is faster, GPT-5.1 Codex or GPT-5 Nano?
GPT-5 Nano is faster, generating output at 250 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 GPT-5 Nano 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.