Gemini 2.5 Pro vs GPT-5.1 Codex
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
Gemini 2.5 Pro by Google wins on 7 of 15 benchmarks against GPT-5.1 Codex 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, Gemini 2.5 Pro scores 1465 on Chatbot Arena ELO compared to GPT-5.1 Codex's 1395, while Gemini 2.5 Pro scores 84.0% on MMLU-Pro compared to GPT-5.1 Codex's 82.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to Gemini 2.5 Pro's 89.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to Gemini 2.5 Pro's 63.8%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to Gemini 2.5 Pro's 58.0%.
Math: In math, Gemini 2.5 Pro scores 88.0% on MATH compared to GPT-5.1 Codex's 85.0%, while Gemini 2.5 Pro scores 95.5% on GSM8K compared to GPT-5.1 Codex's 95.0%.
Reasoning: In reasoning, Gemini 2.5 Pro scores 84.0% 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 Gemini 2.5 Pro's 48.0%.
Context: In context, Gemini 2.5 Pro scores 1.0M on Context Length compared to GPT-5.1 Codex's 400K.
Pricing Comparison
Gemini 2.5 Pro costs $1.3/1M input tokens and $10.0/1M output tokens, while GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output. Both models are priced identically for input tokens.
Speed Comparison
Gemini 2.5 Pro generates output at 55 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 500 ms for Gemini 2.5 Pro versus 400 ms for GPT-5.1 Codex. GPT-5.1 Codex delivers faster throughput.
Verdict
For developers prioritizing general intelligence and math, Gemini 2.5 Pro has the edge. For those who value coding and speed, GPT-5.1 Codex is the stronger choice.
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Gemini 2.5 Pro vs GPT-5.1 Codex — FAQ
Which is better, Gemini 2.5 Pro or GPT-5.1 Codex?
Gemini 2.5 Pro wins on more benchmarks overall (7 vs 6). However, the best choice depends on your specific needs — each model excels in different areas.
How does Gemini 2.5 Pro 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 63.8%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is Gemini 2.5 Pro cheaper than GPT-5.1 Codex?
Both models are priced the same at $1.3/1M input tokens. Gemini 2.5 Pro output costs $10.0/1M and GPT-5.1 Codex output costs $10.0/1M.
Which is faster, Gemini 2.5 Pro or GPT-5.1 Codex?
GPT-5.1 Codex is faster, generating output at 85 tok/s compared to 55 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Gemini 2.5 Pro 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.