GPT-4.1 Nano 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 9 of 15 benchmarks against GPT-4.1 Nano 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 GPT-4.1 Nano's 1120, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to GPT-4.1 Nano's 55.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to GPT-4.1 Nano's 65.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to GPT-4.1 Nano's 18.0%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to GPT-4.1 Nano's 22.0%.
Math: In math, GPT-5.1 Codex scores 85.0% on MATH compared to GPT-4.1 Nano's 55.0%, while GPT-5.1 Codex scores 95.0% on GSM8K compared to GPT-4.1 Nano's 78.0%.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to GPT-4.1 Nano's 28.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to GPT-4.1 Nano's 10.0%.
Context: In context, GPT-4.1 Nano scores 1.0M on Context Length compared to GPT-5.1 Codex's 400K.
Pricing Comparison
GPT-4.1 Nano costs $0.10/1M input tokens and $0.40/1M output tokens, while GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output. GPT-4.1 Nano is the more affordable option for API usage.
Speed Comparison
GPT-4.1 Nano generates output at 200 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 90 ms for GPT-4.1 Nano versus 400 ms for GPT-5.1 Codex. GPT-4.1 Nano delivers faster throughput.
Verdict
For developers prioritizing affordability and speed, GPT-4.1 Nano has the edge. For those who value coding and general intelligence and math, GPT-5.1 Codex is the stronger choice.
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GPT-4.1 Nano vs GPT-5.1 Codex — FAQ
Which is better, GPT-4.1 Nano or GPT-5.1 Codex?
GPT-5.1 Codex wins on more benchmarks overall (9 vs 6). However, the best choice depends on your specific needs — each model excels in different areas.
How does GPT-4.1 Nano 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 18.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is GPT-4.1 Nano cheaper than GPT-5.1 Codex?
Yes, GPT-4.1 Nano is cheaper. GPT-4.1 Nano costs $0.10/1M input and $0.40/1M output tokens. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens.
Which is faster, GPT-4.1 Nano or GPT-5.1 Codex?
GPT-4.1 Nano is faster, generating output at 200 tok/s compared to 85 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the GPT-4.1 Nano 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.