Gemini 3.1 Pro Preview vs Gemini 3.8 Flash.
Verdict by category, tale of the tape, shared benchmarks only, and cost at three workloads — all from the tracked data.
Verdict by category
| Category | Gemini 3.1 Pro Preview | Gemini 3.8 Flash | Winner |
|---|---|---|---|
| League Score | 58.4 | 57.8 | Gemini 3.1 Pro Preview |
| Coding (SWE-bench %) | 75.6 | — | — |
| Reasoning (GPQA %) | 94.3 | 95.0 | Gemini 3.8 Flash |
| Context (tokens) | 1000000 | 1048576 | Gemini 3.8 Flash |
| Speed (tok/s) | — | — | — |
| Price (blended $/1M) | $4.50 | $1.50 | Gemini 3.8 Flash (cheaper) |
Tale of the tape
| Spec | Gemini 3.1 Pro Preview | Gemini 3.8 Flash |
|---|---|---|
| Maker | Google DeepMind | Google DeepMind |
| Released | Feb 19, 2026 | Sep 2, 2026 |
| League Score | 58 | 58 |
| Context | 1,000,000 tokens | 1,048,576 tokens |
| Max output | 65,536 | 65,536 |
| $/1M input | $2.00 | $0.75 |
| $/1M output | $12.00 | $3.75 |
| Weights | Closed | Closed |
| Speed | — | — |
Head-to-head benchmarks (shared only)
| Benchmark | Gemini 3.1 Pro Preview | Gemini 3.8 Flash |
|---|---|---|
| LiveBench overall | 54.9 | 59.2 |
| GPQA Diamond | 94.3 | 95.0 |
Cost at three workloads
| Workload | Gemini 3.1 Pro Preview | Gemini 3.8 Flash |
|---|---|---|
| Light — 1M in / 250K out | $5.00 | $1.69 |
| Standard — 10M in / 2.5M out | $50.00 | $16.88 |
| Long-context — 50M in / 5M out | $160.00 | $56.25 |
The pick
Pick Gemini 3.1 Pro Preview if you want the higher overall League Score; coding is the priority.
Pick Gemini 3.8 Flash if you need the bigger context window; you want the lower running cost.
All figures from the model database — sources and dates on each model page. Cost your own workload or compare a different pair.
Frequently asked questions
Which is better overall, Gemini 3.1 Pro Preview or Gemini 3.8 Flash?
On overall League Score they are effectively tied — Gemini 3.1 Pro Preview scores 58 and Gemini 3.8 Flash scores 58. The category verdicts on this page are where the real differences live.
Which is cheaper, Gemini 3.1 Pro Preview or Gemini 3.8 Flash?
Gemini 3.8 Flash is cheaper: $1.50 vs $4.50 blended per 1M tokens (3:1 input/output mix) — about 3.0x less per token.
Which has the bigger context window, Gemini 3.1 Pro Preview or Gemini 3.8 Flash?
Gemini 3.8 Flash, with 1M of context against 1M for Gemini 3.1 Pro Preview.
Which is better at reasoning, Gemini 3.1 Pro Preview or Gemini 3.8 Flash?
Gemini 3.8 Flash leads on GPQA Diamond, 95.0% vs 94.3% on graduate-level science questions.
Are Gemini 3.1 Pro Preview and Gemini 3.8 Flash open source?
Gemini 3.1 Pro Preview is closed weights — API access only; Gemini 3.8 Flash is closed weights — API access only.