Gemini 2.5 Flash vs Gemini 3.1 Pro
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
Gemini 3.1 Pro by Google wins on 9 of 14 benchmarks against Gemini 2.5 Flash by Google, which leads on 5. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from the AI Value Index.
Category-by-Category Breakdown
General Intelligence: In general intelligence, Gemini 3.1 Pro scores 1501 on Chatbot Arena ELO compared to Gemini 2.5 Flash's 1320, while Gemini 3.1 Pro scores 92.6% on MMLU-Pro compared to Gemini 2.5 Flash's 73.0%.
Coding: In coding, Gemini 3.1 Pro scores 93.0% on HumanEval+ compared to Gemini 2.5 Flash's 82.0%, while Gemini 3.1 Pro scores 80.6% on SWE-bench Verified compared to Gemini 2.5 Flash's 38.0%, while Gemini 3.1 Pro scores 75.0% on LiveCodeBench compared to Gemini 2.5 Flash's 42.0%.
Math: In math, Gemini 3.1 Pro scores 93.0% on MATH compared to Gemini 2.5 Flash's 76.0%, while Gemini 3.1 Pro scores 98.0% on GSM8K compared to Gemini 2.5 Flash's 91.0%.
Reasoning: In reasoning, Gemini 3.1 Pro scores 94.1% on GPQA Diamond compared to Gemini 2.5 Flash's 48.0%, while Gemini 3.1 Pro scores 77.1% on ARC-AGI compared to Gemini 2.5 Flash's 25.0%.
Context: In context, Gemini 2.5 Flash scores 1.0M on Context Length compared to Gemini 3.1 Pro's 1.0M.
Pricing Comparison
Gemini 2.5 Flash costs $0.30/1M input tokens and $2.5/1M output tokens, while Gemini 3.1 Pro costs $2.0/1M input and $12.0/1M output. Gemini 2.5 Flash is the more affordable option for API usage.
Speed Comparison
Gemini 2.5 Flash generates output at 251 tok/s compared to Gemini 3.1 Pro's 65 tok/s, and the time to first token is 410 ms for Gemini 2.5 Flash versus 420 ms for Gemini 3.1 Pro. Gemini 2.5 Flash delivers faster throughput.
Verdict
For developers prioritizing affordability and speed, Gemini 2.5 Flash has the edge. For those who value coding and general intelligence and math, Gemini 3.1 Pro is the stronger choice.
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Gemini 2.5 Flash vs Gemini 3.1 Pro — FAQ
Which is better, Gemini 2.5 Flash or Gemini 3.1 Pro?
Gemini 3.1 Pro 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 Gemini 2.5 Flash compare to Gemini 3.1 Pro for coding?
Gemini 3.1 Pro is better for coding, scoring 80.6% on SWE-bench Verified compared to 38.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is Gemini 2.5 Flash cheaper than Gemini 3.1 Pro?
Yes, Gemini 2.5 Flash is cheaper. Gemini 2.5 Flash costs $0.30/1M input and $2.5/1M output tokens. Gemini 3.1 Pro costs $2.0/1M input and $12.0/1M output tokens.
Which is faster, Gemini 2.5 Flash or Gemini 3.1 Pro?
Gemini 2.5 Flash is faster, generating output at 251 tok/s compared to 65 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Gemini 2.5 Flash vs Gemini 3.1 Pro comparison cover?
This comparison covers 14 benchmarks including Chatbot Arena ELO, MMLU-Pro, HumanEval+, MATH, SWE-bench Verified, GPQA Diamond, Output Speed, Time to First Token, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.