Google: Gemini 3.5 Flash vs Google: Gemini 3.1 Pro Preview
Side-by-side comparison of specs, pricing, benchmark scores, and task rankings. Updated 2026-11-07.
| Google: Gemini 3.5 Flash | Google: Gemini 3.1 Pro Preview | |
|---|---|---|
| Vendor | ||
| Quality Score | 100 | 100 |
| Benchmark Score | 84.2 | 74.7 |
| Input Price | $1.50/M | $2.00/M |
| Output Price | $9.00/M | $12.00/M |
| Context Window | 1,048,576 | 1,048,576 |
| Max Output | 65,536 | 65,536 |
| Tool Calling | ✓ | ✓ |
| Structured Output | ✓ | ✓ |
| Reasoning Mode | ✓ | ✓ |
| Vision | ✓ | ✓ |
| Audio | ✓ | ✓ |
| Benchmark Scores | ||
| ai_index | 82.8 | 76.7 |
| ai_index_agentic | 61.8 | 35.3 |
| ai_index_coding | 100.0 | 100.0 |
| eqbench | - | 64.7 |
The verdict
For a sample job of 1 million input tokens and 250,000 output tokens, Gemini 3.5 Flash costs $3.75 and Gemini 3.1 Pro Preview costs $5.00, so Gemini 3.5 Flash is about 1.3 times cheaper for the same work.
Both read up to 1,048,576 tokens at once, roughly 1,573 pages of text.
On our blended benchmark score Gemini 3.5 Flash leads 84.2 to 74.7.
Across the 19 tasks where they differ, Gemini 3.5 Flash scores higher on 6 (SQL Generation, Regex Writing, Data Analysis and others), Gemini 3.1 Pro Preview on 13 (Code Review, Code Completion, Code Refactoring and others).
Gemini 3.5 Flash was released in May 2026 and Gemini 3.1 Pro Preview in February 2026.
Pick Gemini 3.5 Flash if you need lower cost or benchmark performance; pick Gemini 3.1 Pro Preview if you need the stronger all-round task scores.
Costs use current list prices per million tokens; page counts assume about 0.75 words per token and 500 words per page.
Who wins by task?
| Task | Google: Gemini 3.5 Flash | Google: Gemini 3.1 Pro Preview |
|---|---|---|
| SQL Generation | 168 | 168 |
| Code Review | 164 | 168 |
| Code Completion | 119 | 120 |
| Code Refactoring | 162 | 168 |
| Bug Fixing | 176 | 177 |
| Unit Test Generation | 152 | 154 |
| Code Documentation | 141 | 144 |
| Regex Writing | 133 | 133 |
| CI/CD Pipelines | 143 | 145 |
| Data Analysis | 167 | 164 |
| CSV / Spreadsheet Cleanup | 153 | 155 |
| ETL Scripting | 152 | 156 |
| JSON Extraction | 138 | 137 |
| Bulk Data Labeling | 124 | 123 |
| OCR / Document Parsing | 146 | 147 |
| Table Extraction from PDFs | 146 | 147 |
| Long-Document Summarization | 157 | 163 |
| Short-Form Summarization | 121 | 121 |
| Blog Post Writing | 138 | 140 |
Scores reflect capability match + benchmark data + pricing for each task. Methodology →