Gemini 3.1 Pro vs Gemini 3.5 Flash
Gemini 3.1 Pro and Gemini 3.5 Flash are closely matched at 43.2 and 42.4 on the LLM Stats Score. Gemini 3.5 Flash is 1.3x cheaper per token.
Google · Google · Updated for 2026
Which is better?
Gemini 3.1 Pro and Gemini 3.5 Flash are closely matched on the overall LLM Stats Score at 43.2 and 42.4.
In the 11 individual benchmarks reported for both models, Gemini 3.5 Flash wins 8; this is a narrower head-to-head signal than the composite indexes.
On price, Gemini 3.5 Flash is roughly 1.3x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Gemini 3.1 Pro
- you want predictable pricing at $2.00/M input and $12.00/M output
Choose Gemini 3.5 Flash
- you value its reported benchmark strengths — it wins 8 of 11 exact shared results
- cost matters — it's about 1.3x cheaper per token
- you want the most recent training data — it shipped May 2026
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
20 reported for Gemini 3.1 Pro · 16 for Gemini 3.5 Flash
Gemini 3.1 Pro outperforms in 3 benchmarks (ARC-AGI v2, Humanity's Last Exam, LiveBench), while Gemini 3.5 Flash is better at 8 benchmarks (DeepSWE 1.1, Finance Agent v2, Legal Agent Benchmark, MCP Atlas, MMMU-Pro, MRCR v2 (8-needle), SWE-Bench Pro, Terminal-Bench 2.0).
Gemini 3.5 Flash shows notably better performance in the majority of benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Gemini 3.1 Pro ($2.00/1M tokens) is 1.3x more expensive than Gemini 3.5 Flash ($1.50/1M tokens).
For output processing, Gemini 3.1 Pro ($12.00/1M tokens) is 1.3x more expensive than Gemini 3.5 Flash ($9.00/1M tokens).
In conclusion, Gemini 3.1 Pro is more expensive than Gemini 3.5 Flash.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Both models have the same input context window of 1,000,000 tokens. Both models can generate responses up to 1,000,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Gemini 3.1 Pro and Gemini 3.5 Flash support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Gemini 3.1 Pro
Gemini 3.5 Flash
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Gemini 3.1 Pro was released on 2026-02-19, while Gemini 3.5 Flash was released on 2026-05-19.
Gemini 3.5 Flash is 3 months newer than Gemini 3.1 Pro.
Feb 19, 2026
7 months ago
May 19, 2026
4 months ago
2mo newerKnowledge Cutoff
When training data ends
Gemini 3.1 Pro has a knowledge cutoff of 2025-01-31, while Gemini 3.5 Flash has a cutoff of 2026-01-31.
Gemini 3.5 Flash has more recent training data (up to 2026-01-31), making it potentially better informed about events through that date compared to Gemini 3.1 Pro (2025-01-31).
Jan 2025
Jan 2026
1 yr newerProvider Availability
Gemini 3.1 Pro is available from DeepInfra, Google. Gemini 3.5 Flash is available from DeepInfra, Google.
Gemini 3.1 Pro
Gemini 3.5 Flash
Outputs Comparison
Judge for yourself.
Run your own prompts against Gemini 3.1 Pro and Gemini 3.5 Flash side-by-side, then vote on the output you prefer.
FAQ
Common questions about Gemini 3.1 Pro vs Gemini 3.5 Flash.