Gemini 3.1 Pro vs Grok 4.5
Both are Flagship-tier models, from Google and xAI respectively. Grok 4.5 is the cheaper choice overall at a 4:1 input:output ratio.
Which is cheaper
Side by side
| Spec | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Provider | xAI | |
| Tier | Flagship | Flagship |
| Context window | 1M | 500K |
| Max output | 66K | — |
| Input $/1M | $2.00 | $2.00 |
| Output $/1M | $12.00 | $6.00 |
| Cache read $/1M | $0.20 | $0.30 |
| Modalities | text, image | text, image |
Gemini 3.1 Pro. Listed as gemini-3.1-pro-preview. Standard tier for prompts up to 200K tokens; above that, $4 input / $18 output and $0.40 cache read per 1M. Cached context is also billed for storage at $4.50 per 1M tokens per hour.
Grok 4.5. Short-context rate, for prompts under 200K tokens. At 200K and above: $4 input / $12 output, cache read $0.60 per 1M. Same input and output price as Grok 4.6 with a cheaper cache read; the previous flagship, not marked deprecated.
Sources
Gemini 3.1 Pro — verified August 29, 2026
Grok 4.5 — verified August 29, 2026
Full Gemini 3.1 Pro pricing page → · Full Grok 4.5 pricing page →