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Gemini 3.1 Pro Preview versus Gemini 3.5 Flash on price, context, and capabilities. Both are in the Google group. Costs use a shared reference workload. Prices from Models.dev. Data last refreshed Oct 16, 2026, 07:15 AM UTC.

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Gemini 3.1 Pro PreviewvsGemini 3.5 Flash

Alphabetical by model id, so this URL is the one to index. Gemini 3.1 Pro Preview is google/gemini-3.1-pro-preview. Gemini 3.5 Flash is google/gemini-3.5-flash. Both are among the models the most providers list, inside the Google group.

vs

100 requests a day, 2,000 input tokens and 500 output tokens, no cache hits. A light chat workload so the rate cards are comparable.
SpecGemini 3.1 Pro PreviewGemini 3.5 Flash
Monthly, reference workload$30.00$22.50
Input / 1M$2.00$1.50
Output / 1M$12.00$9.00
Cache read / 1M$0.20$0.15
Cache write / 1M——
Context1,048,5761,048,576
Max output65,53665,536
ReasoningYesYes
Tool callsYesYes
VisionYesYes
Open weightsNoNo
Providers2934
Released2026-02-192026-05-19

Same workload, your numbers

Prices are USD per 1M tokens. A month is 30 days. Cache hits use the cache-read rate when the model has one; otherwise the cache field is ignored.

Gemini 3.1 Pro Preview costs $7.50 more per month than Gemini 3.5 Flash at these inputs.

monthly = requests/day × 30 × (input tokens × (1 − cache hit) × input price + input tokens × cache hit × cache-read price + output tokens × output price) ÷ 1,000,000