OpenAI: o3 Pro vs xAI: Grok 4
Head-to-head API pricing and cost comparison between OpenAI’s OpenAI: o3 Pro and xAI’s xAI: Grok 4. Prices auto-refresh daily from OpenRouter.
xAI: Grok 4 is 85% cheaper for input tokens; xAI: Grok 4 also wins on output tokens.
Side-by-side comparison
| Spec | OpenAI: o3 Pro | xAI: Grok 4 |
|---|---|---|
| Input price (per 1M) | $20.00 | $3.00 |
| Cached input (per 1M) | — | $0.75 |
| Output price (per 1M) | $80.00 | $15.00 |
| Batch input (per 1M) | $10.00 | — |
| Batch output (per 1M) | $40.00 | — |
| Reasoning price (per 1M) | — | — |
| Context window | 200K | 256K |
| Vision support | Yes | Yes |
| Caching support | No | Yes |
| Batch API | Yes | No |
| Reasoning capability | Yes | No |
Monthly cost at volume
Estimated monthly API spend at common production traffic levels (input/output tokens per request shown).
| Volume | OpenAI: o3 Pro | xAI: Grok 4 | Savings |
|---|---|---|---|
1K req/day 500in / 200out tokens | $780.00 | $135.00 | $645.00 xAI: Grok 4 wins |
10K req/day 1500in / 500out tokens | $21,000 | $3,600 | $17,400 xAI: Grok 4 wins |
100K req/day 3000in / 800out tokens | $372,000 | $63,000 | $309,000 xAI: Grok 4 wins |
1M req/day 8000in / 2000out tokens | $9,600,000 | $1,620,000 | $7,980,000 xAI: Grok 4 wins |
Adjust input/output token counts, request volume, batch & cached pricing.
Related comparisons
Frequently asked questions
Which is cheaper, OpenAI: o3 Pro or xAI: Grok 4?
For input tokens, xAI: Grok 4 is roughly 85% cheaper at $3.00/1M vs $20.00/1M. For output tokens, xAI: Grok 4 wins at $15.00/1M. Real-world cost depends on your input/output ratio — use the calculator to model your actual workload.
What’s the context window difference?
OpenAI: o3 Pro has a context window of 200K tokens. xAI: Grok 4 offers 256K tokens. Larger context windows are valuable for long documents, RAG pipelines, and multi-turn conversations — but they come with higher input-token bills if you fill them every request.
Should I use OpenAI: o3 Pro or xAI: Grok 4?
Choose OpenAI: o3 Pro if you’re already on the OpenAI stack, want reasoning capabilities, or prefer its feature set. Choose xAI: Grok 4 for xAI’s ecosystem, native vision input, or its cheaper input tokens. Run a small benchmark on your own prompts before committing — price is only one axis.
How are these prices kept current?
Prices are pulled directly from OpenRouter’s public models API once every 24 hours via a Convex cron job, then normalized to per-1M-token figures. Last refresh: Apr 21, 2026.