Gemini 3.1 Pro Preview Custom Tools vs Gemini 3 Flash Preview
Gemini 3 Flash Preview costs 4.0x less per output token than Gemini 3.1 Pro Preview Custom Tools ($3.00 vs $12.00 per million). Updated October 21, 2026; 1 benchmarks have a result for both.
Gemini 3.1 Pro Preview Custom Tools or Gemini 3 Flash Preview: which to pick
Only Gemini 3 Flash Preview has a coding score, 43.7 on the Vibe Coding Index; Gemini 3.1 Pro Preview Custom Tools has none, so the two cannot be ranked on coding.
Pick Gemini 3.1 Pro Preview Custom Tools for work measured by Vending-Bench 2, where it leads.
- Shared results
- 1
- Gemini 3.1 Pro Preview Custom Tools only
- 0
- Gemini 3 Flash Preview only
- 68
- Like-for-like categories
- 1 of 9
Only benchmarks that tested both models count toward a pick; a result only one model has is shown but not compared.
Which one for your work
Each card is decided by one number both models carry. Where only one has it, the card says so and makes no call.
Coding
Vibe Coding Index, six public coding benchmarks
No call
Only Gemini 3 Flash Preview has a coding score, so no call is made.
One side not measured
Intelligence
AA Intelligence Index
No call
Only Gemini 3 Flash Preview has a AA Intelligence Index result, 26.3.
Directional only
Reasoning
GPQA Diamond
No call
Only Gemini 3 Flash Preview has a GPQA Diamond result, 87.9%.
Directional only
Math
AIME
No call
Only Gemini 3 Flash Preview has a AIME result, 95.6%.
Directional only
Knowledge
MMLU Pro
No call
Only Gemini 3 Flash Preview has a MMLU Pro result, 88.6%.
Directional only
Web design
Design Arena: websites
No call
Only Gemini 3 Flash Preview has a Design Arena: websites result, 1196.
Directional only
Long documents
Listed context window
No call
Both take 1.05M tokens.
Listed by OpenRouter
Everyday cost
1K input + 500 output tokens
Gemini 3 Flash Preview
Gemini 3.1 Pro Preview Custom Tools $0.0080, Gemini 3 Flash Preview $0.0020 per turn.
List prices
Cost per solved task
One SWE-bench Verified task, solved
No call
Only Gemini 3 Flash Preview has the number, $0.37.
Directional only
At a glance
- Coding index
- Gemini 3.1 Pro Preview Custom Tools not benchmarked, Gemini 3 Flash Preview 43.7 from 2 benchmarks.
- Widest category
- Agentic work, 0.9 points apart on average over 1 shared benchmark.
- Widest single gap
- Vending-Bench 2: Gemini 3.1 Pro Preview Custom Tools $3,774 against Gemini 3 Flash Preview $3,635, 0.9 points apart on a 0 to 100 scale.
- Output price
- Gemini 3.1 Pro Preview Custom Tools $12.00 against Gemini 3 Flash Preview $3.00 per million output tokens, 4.0x apart.
- Context window
- Both take 1.05M tokens.
Benchmark by benchmark
First the score: boards each model leads, per category, where both have a result. Then every board, a category to a fold; bars are each result on a 0 to 100 scale, so compare the two in a row, not one row with another.
| Category | Gemini 3.1 Pro Preview Custom Tools | Bars | Gemini 3 Flash Preview | Ties |
|---|---|---|---|---|
| Agentic work | 1 | 0 | ||
| All shared boards | 1 | 0 |
CodingDirectional onlySix of these boards feed the Vibe Coding Index13 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| SWE-bench Verified | Not measured | 75.8% | Only Gemini 3 Flash Preview measured |
| LiveCodeBench (Vals AI) | Not measured | 85.6% | Only Gemini 3 Flash Preview measured |
| SWE-bench Verified (Vals AI) | Not measured | 75.0% | Only Gemini 3 Flash Preview measured |
| Vibe Code Bench (Vals AI) | Not measured | 20.2% | Only Gemini 3 Flash Preview measured |
| Code migration (Vals AI) | Not measured | 6.4% | Only Gemini 3 Flash Preview measured |
| ProgramBench (Vals AI) | Not measured | 0.0% | Only Gemini 3 Flash Preview measured |
| Terminal-Bench 2.1 (Vals AI) | Not measured | 53.9% | Only Gemini 3 Flash Preview measured |
| LiveCodeBench (Artificial Analysis run) | Not measured | 90.8% | Only Gemini 3 Flash Preview measured |
| Terminal-Bench Hard (Artificial Analysis run) | Not measured | 38.6% | Only Gemini 3 Flash Preview measured |
| Terminal-Bench | Not measured | 64.3% | Only Gemini 3 Flash Preview measured |
| GSO-Bench | Not measured | 9.8% | Only Gemini 3 Flash Preview measured |
| WeirdML | Not measured | 61.6% | Only Gemini 3 Flash Preview measured |
| ALE-Bench | Not measured | 1367.2 | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 25 boards here | |||
IntelligenceDirectional onlyPublic boards, shown as published, kept out of the index1 board, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| AA Intelligence Index | Not measured | 26.3 | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 1 board here | |||
Agentic workLike-for-likePublic boards, shown as published, kept out of the index10
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| Design Arena: agents building web apps | Not measured | 1110 | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building full-stack apps | Not measured | 1063 | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building mobile apps | Not measured | 1090 | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building Android apps | Not measured | 1050 | Only Gemini 3 Flash Preview measured |
| Design Arena: agents building Godot games | Not measured | 1161 | Only Gemini 3 Flash Preview measured |
| Design Arena: PowerPoint slides | Not measured | 1036 | Only Gemini 3 Flash Preview measured |
| Finance Agent (Vals AI) | Not measured | 42.5% | Only Gemini 3 Flash Preview measured |
| Tax Agent Bench (Vals AI) | Not measured | 11.8% | Only Gemini 3 Flash Preview measured |
| Legal Research Bench (Vals AI) | Not measured | 18.3% | Only Gemini 3 Flash Preview measured |
| Excel Modeling Benchmark (Vals AI) | Not measured | 26.0% | Only Gemini 3 Flash Preview measured |
| τ²-Bench Telecom | Not measured | 80.4% | Only Gemini 3 Flash Preview measured |
| BALROG | Not measured | 48.1% | Only Gemini 3 Flash Preview measured |
| DeepResearch Bench | Not measured | 49.8% | Only Gemini 3 Flash Preview measured |
| Vending-Bench 2 | $3,774 | $3,635 | Gemini 3.1 Pro Preview Custom Tools |
| Neither model has a result on the other 25 boards here | |||
ReasoningDirectional onlyPublic boards, shown as published, kept out of the index11 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| GPQA Diamond | Not measured | 87.9% | Only Gemini 3 Flash Preview measured |
| MMMU Pro (Vals AI) | Not measured | 87.6% | Only Gemini 3 Flash Preview measured |
| GPQA Diamond (Artificial Analysis run) | Not measured | 89.8% | Only Gemini 3 Flash Preview measured |
| Humanity's Last Exam (Artificial Analysis run) | Not measured | 36.6% | Only Gemini 3 Flash Preview measured |
| GPQA Diamond (Epoch AI run) | Not measured | 89.4% | Only Gemini 3 Flash Preview measured |
| ARC-AGI | Not measured | 84.7% | Only Gemini 3 Flash Preview measured |
| ARC-AGI-2 | Not measured | 33.6% | Only Gemini 3 Flash Preview measured |
| SimpleBench | Not measured | 61.1% | Only Gemini 3 Flash Preview measured |
| Chess puzzles | Not measured | 39.0% | Only Gemini 3 Flash Preview measured |
| Mystery game puzzles | Not measured | 26.0% | Only Gemini 3 Flash Preview measured |
| VPCT | Not measured | 72.6% | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 10 boards here | |||
MathDirectional onlyPublic boards, shown as published, kept out of the index8 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| AIME | Not measured | 95.6% | Only Gemini 3 Flash Preview measured |
| MGSM (Vals AI) | Not measured | 93.3% | Only Gemini 3 Flash Preview measured |
| AA Math Index | Not measured | 97.0 | Only Gemini 3 Flash Preview measured |
| AIME 2025 (Artificial Analysis run) | Not measured | 97.0% | Only Gemini 3 Flash Preview measured |
| OTIS Mock AIME | Not measured | 95.6% | Only Gemini 3 Flash Preview measured |
| FrontierMath, tiers 1 to 3 | Not measured | 51.2% | Only Gemini 3 Flash Preview measured |
| FrontierMath, tier 4 | Not measured | 17.1% | Only Gemini 3 Flash Preview measured |
| ProofBench | Not measured | 15.0% | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 5 boards here | |||
KnowledgeDirectional onlyPublic boards, shown as published, kept out of the index11 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| MMLU Pro | Not measured | 88.6% | Only Gemini 3 Flash Preview measured |
| LegalBench (Vals AI) | Not measured | 86.9% | Only Gemini 3 Flash Preview measured |
| CaseLaw (Vals AI) | Not measured | 55.8% | Only Gemini 3 Flash Preview measured |
| CorpFin (Vals AI) | Not measured | 66.4% | Only Gemini 3 Flash Preview measured |
| TaxEval (Vals AI) | Not measured | 73.9% | Only Gemini 3 Flash Preview measured |
| MortgageTax (Vals AI) | Not measured | 68.7% | Only Gemini 3 Flash Preview measured |
| MedQA (Vals AI) | Not measured | 95.8% | Only Gemini 3 Flash Preview measured |
| MedCode (Vals AI) | Not measured | 55.9% | Only Gemini 3 Flash Preview measured |
| MMLU Pro (Artificial Analysis run) | Not measured | 89.0% | Only Gemini 3 Flash Preview measured |
| SimpleQA Verified | Not measured | 66.8% | Only Gemini 3 Flash Preview measured |
| GeoBench | Not measured | 88.0% | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 6 boards here | |||
Web designDirectional onlyPublic boards, shown as published, kept out of the index4 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| Design Arena: websites | Not measured | 1196 | Only Gemini 3 Flash Preview measured |
| Design Arena: game dev | Not measured | 1166 | Only Gemini 3 Flash Preview measured |
| Design Arena: 3D | Not measured | 1184 | Only Gemini 3 Flash Preview measured |
| Design Arena: all code categories | Not measured | 1189 | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 5 boards here | |||
GeneralDirectional onlyPublic boards, shown as published, kept out of the index7 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| SAGE (Vals AI) | Not measured | 51.8% | Only Gemini 3 Flash Preview measured |
| MedScribe (Vals AI) | Not measured | 69.9% | Only Gemini 3 Flash Preview measured |
| Vals Multimodal Index | Not measured | 52.2% | Only Gemini 3 Flash Preview measured |
| IFBench | Not measured | 78.0% | Only Gemini 3 Flash Preview measured |
| Long context reasoning (AA-LCR) | Not measured | 78.0% | Only Gemini 3 Flash Preview measured |
| DTBench | Not measured | 89.1% | Only Gemini 3 Flash Preview measured |
| LMCA | Not measured | 43.1% | Only Gemini 3 Flash Preview measured |
| Neither model has a result on the other 39 boards here | |||
Image generationNot comparablePublic boards, shown as published, kept out of the index0 boards, none shared
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | Gemini 3 Flash Preview | Leader |
|---|---|---|---|
| Neither model has a result on 5 boards here | |||
What each workload costs
Three fixed token mixes at each model's listed price, so per-token rates become a bill.
Chat turn
1K input + 500 output tokens
Gemini 3 Flash Preview costs less
Repository review
50K input + 3K output tokens
Gemini 3 Flash Preview costs less
Agent loop
200K input + 10K output tokens
Gemini 3 Flash Preview costs less
Listed OpenRouter rates, without cache or batch discounts. A workload that does not fit a model's context window would need splitting.
Specification differences
The leading value in a row is marked; a row with a missing value names no leader. Our two rows are marked in red.
| Specification | Google Gemini 3.1 Pro Preview Custom Tools | Google Gemini 3 Flash Preview |
|---|---|---|
| Maker | ||
| Weights | No public weights listed | No public weights listed |
| Released | February 25, 2026 | December 17, 2025 |
| Context window | 1.05M | 1.05M |
| Input $/Mtok | $2.00 | $0.50 |
| Output $/Mtok | $12.00 | $3.00 |
| Coding index | Not benchmarked | 43.7 |
| Independent measurements behind it | 0 | 2 |
| Cost per solved task | Not computable | $0.37 |
| Source | OpenRouter listing | OpenRouter listing |
Questions
Is Gemini 3.1 Pro Preview Custom Tools better than Gemini 3 Flash Preview for coding?
Only Gemini 3 Flash Preview has a coding score, 43.7 on the Vibe Coding Index; Gemini 3.1 Pro Preview Custom Tools has none, so the two cannot be ranked on coding. Pick Gemini 3.1 Pro Preview Custom Tools for work measured by Vending-Bench 2, where it leads.
Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or Gemini 3 Flash Preview?
Gemini 3.1 Pro Preview Custom Tools costs $2.00 per million input tokens and $12.00 per million output tokens; Gemini 3 Flash Preview costs $0.50 and $3.00. Cost per solved task is known for Gemini 3 Flash Preview only.
Which has the bigger context window, Gemini 3.1 Pro Preview Custom Tools or Gemini 3 Flash Preview?
Neither: both take 1.05M tokens.
How many benchmarks is the Gemini 3.1 Pro Preview Custom Tools vs Gemini 3 Flash Preview comparison based on?
1 benchmarks have a result for both models as of October 21, 2026. Gemini 3.1 Pro Preview Custom Tools's coding index rests on 0 independent benchmarks and Gemini 3 Flash Preview's on 2. Where only one model has a result, the page says so instead of naming a winner.