Gemini 2.5 Flash Lite 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 Gemini 2.5 Flash Lite by Google, 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 Gemini 2.5 Flash Lite's 1230, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to Gemini 2.5 Flash Lite's 63.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to Gemini 2.5 Flash Lite's 70.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to Gemini 2.5 Flash Lite's 22.0%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to Gemini 2.5 Flash Lite's 28.0%.
Math: In math, GPT-5.1 Codex scores 85.0% on MATH compared to Gemini 2.5 Flash Lite's 62.0%, while GPT-5.1 Codex scores 95.0% on GSM8K compared to Gemini 2.5 Flash Lite's 83.0%.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to Gemini 2.5 Flash Lite's 32.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to Gemini 2.5 Flash Lite's 14.0%.
Context: In context, Gemini 2.5 Flash Lite scores 1.0M on Context Length compared to GPT-5.1 Codex's 400K.
Pricing Comparison
Gemini 2.5 Flash Lite 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. Gemini 2.5 Flash Lite is the more affordable option for API usage.
Speed Comparison
Gemini 2.5 Flash Lite generates output at 240 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 70 ms for Gemini 2.5 Flash Lite versus 400 ms for GPT-5.1 Codex. Gemini 2.5 Flash Lite delivers faster throughput.
Verdict
For developers prioritizing affordability and speed, Gemini 2.5 Flash Lite 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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Gemini 2.5 Flash Lite vs GPT-5.1 Codex — FAQ
Which is better, Gemini 2.5 Flash Lite 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 Gemini 2.5 Flash Lite 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 22.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is Gemini 2.5 Flash Lite cheaper than GPT-5.1 Codex?
Yes, Gemini 2.5 Flash Lite is cheaper. Gemini 2.5 Flash Lite 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, Gemini 2.5 Flash Lite or GPT-5.1 Codex?
Gemini 2.5 Flash Lite is faster, generating output at 240 tok/s compared to 85 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Gemini 2.5 Flash Lite 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.