Gemini 3.1 Pro vs Grok 4.5 — Price, Context, and Capability Compared
Gemini 3.1 Pro vs Grok 4.5: which should I use?
Gemini 3.1 Pro costs 1.5× more per blended million tokens than Grok 4.5. Gemini 3.1 Pro has the larger context window (2,000,000 tokens). Default to Grok 4.5 unless you specifically need Gemini 3.1 Pro's edge.
Price, speed, and task evidence
Task verdict
Best-fit task signals from the published model strengths; this is not a substitute for a controlled benchmark.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Best fit | Whole-codebase, whole-document, or long-video analysis in a single request. | Agentic software engineering and workflow automation that need strong coding capability at a competitive price. |
| Reasoning mode | Available | Available |
Effective workload cost
Modeled for Coding Agent: 20,000 input + 2,000 output tokens per task, 1 turn. This is a workload model, not a provider quote.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Coding Agent / task | $0.06 (modeled) | $0.05 (modeled) (winner) |
| Input / output rate | $2.00 / $12.00 per M | $2.00 / $6.00 per M |
Speed
Only non-estimated benchmark results are shown as measured.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Measured throughput | 55 tokens/s | Unavailable |
| Time to first token | 420 ms | Unavailable |
API compatibility
Provider-level wire-format and SDK facts; model-specific parameter differences may still apply.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| OpenAI SDK | Not drop-in | Usable |
| Request shape | contents/parts structure instead of messages; an OpenAI-compatible endpoint exists but only covers a subset of parameters. | Full OpenAI chat/completions compatibility — point the openai SDK at api.x.ai and it works unmodified. |
| Streaming | SSE (Gemini streamGenerateContent) | SSE (OpenAI delta) |
Privacy and retention
Provider policy and residency facts from the verified provider registry. A missing retention policy is not treated as a guarantee.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Provider says API data trains models | No | Unavailable |
| Published retention period | Unavailable | Unavailable |
| Data residency | Global by default; Vertex AI offers selectable regional endpoints | Unavailable |
Migration effort
Direction is from each displayed model to the other. Effort is derived from provider compatibility and published parameter maps.
| Fact | Gemini 3.1 Pro | Grok 4.5 |
|---|---|---|
| Move Gemini 3.1 Pro → Grok 4.5 | config; 2 breaking parameter differences | Target: Grok 4.5 |
| Move Grok 4.5 → Gemini 3.1 Pro | Source: Grok 4.5 | code-change; 1 breaking parameter difference |
| Why | Keep the `openai` SDK; change `baseURL` and the API key. | contents/parts structure instead of messages; an OpenAI-compatible endpoint exists but only covers a subset of parameters. |
Spec comparison
| Gemini 3.1 Pro | Grok 4.5 | |
|---|---|---|
| Price (input) | $2.00/M | $2.00/M |
| Price (output) | $12.00/M | $6.00/M ✓ |
| Blended price | $4.50/M | $3.00/M ✓ |
| Context window | 2,000,000 tokens ✓ | 500,000 tokens |
| Max output | 64,000 tokens | 64,000 tokens |
| Modalities | text, vision, audio | text, vision |
| Reasoning mode | Yes | Yes |
| Released | 2026-02 | 2026-07 |
| Speed | 55 t/s | Not measured |
Cost at scale (3:1 blended)
| Tokens / month | Gemini 3.1 Pro | Grok 4.5 | Delta |
|---|---|---|---|
| 1,000,000 | $4.50 | $3.00 | $1.50 (1.5×) |
| 10,000,000 | $45.00 | $30.00 | $15.00 (1.5×) |
| 100,000,000 | $450.00 | $300.00 | $150.00 (1.5×) |
Choose Gemini 3.1 Pro if…
- ✓Largest context window of any current model (2M tokens)
- ✓Native audio and video understanding
- ✓Google Search grounding
- ✓Whole-codebase, whole-document, or long-video analysis in a single request.
Choose Grok 4.5 if…
- ✓xAI coding model for agents and engineering
- ✓Configurable reasoning for complex tasks
- ✓500K-token context at $2/$6 per million tokens
- ✓Agentic software engineering and workflow automation that need strong coding capability at a competitive price.
Run this exact matchup right now
Send the same prompt to Gemini 3.1 Pro and Grok 4.5 side by side and see the outputs yourself.
Try Gemini 3.1 Pro vs Grok 4.5 FreeFAQ
Is Gemini 3.1 Pro cheaper than Grok 4.5?
Grok 4.5 is cheaper, at $3.00 per million blended tokens vs $4.50 for Gemini 3.1 Pro.
Which has the bigger context window, Gemini 3.1 Pro or Grok 4.5?
Gemini 3.1 Pro has the larger context window: 2,000,000 tokens vs 500,000.
Can Gemini 3.1 Pro replace Grok 4.5 for coding?
Both are viable for coding. Largest context window of any current model (2M tokens) (Gemini 3.1 Pro) vs xAI coding model for agents and engineering (Grok 4.5) — pick based on which strength matters more for your workload.
Neither of these? See Gemini 3.1 Pro alternatives or Grok 4.5 alternatives.
Related
Pricing verified 2026-04-06. Specs verified 2026-08-14.