GPT-5.1 vs Grok 4.20
Pricing verdict: GPT-5.1 vs Grok 4.20: input pricing is tied at $1.25/M, Grok 4.20 is cheaper for output-heavy usage ($2.50/M output), and Grok 4.20 is better for long-context tasks (2,000,000 tokens).
Direct answer: input pricing is tied. Choose Grok 4.20 for cheaper output and choose Grok 4.20 when your workload needs longer context.
Compare API pricing, input and output token costs, context windows, and monthly estimates on one page so you can pick the right model fast.
Cost Comparison (1000 input + 500 output tokens, 100 requests/day)
GPT-5.1
Grok 4.20
Cost Differences
Grok 4.20 costs less than GPT-5.1
Quick Recommendation
Winner for direct API pricing: Grok 4.20. At the default workload, Grok 4.20 saves about $11.25/month ($136.875/year) versus GPT-5.1.
Feature Comparison
| Feature | GPT-5.1 | Grok 4.20 |
|---|---|---|
| Provider | OpenAI | xAI |
| Input Price | $1.25/1M tokens | $1.25/1M tokens |
| Output Price | $10.00/1M tokens | $2.50/1M tokens |
| Context Window | 1,000,000 tokens | 2,000,000 tokens |
| Max Output | 131,072 tokens | 131,072 tokens |
| Category | flagship | reasoning |
| Capabilities | textvisionaudiocodereasoning | textvisionreasoningcode |
| Release Date | 11/12/2025 | 2/17/2026 |
GPT-5.1 vs Grok 4.20: Which Should You Choose?
Choosing between GPT-5.1 and Grok 4.20 depends on your priorities: cost efficiency, context length, or raw capability. Both models charge $1.25/1M input tokens, but Grok 4.20 is cheaper on output at $2.50/1M. Meanwhile, Grok 4.20 offers a significantly larger context window at 2,000,000 tokens vs 1,000,000 for GPT-5.1.
These models come from different providers — OpenAI and xAI — which means different API ecosystems, SDKs, rate limits, and terms of service. If you're already integrated with OpenAI, switching to xAIinvolves migration effort beyond just pricing. Factor in your existing infrastructure when deciding.
These models target different tiers: GPT-5.1 is a flagship model while Grok 4.20 is reasoning. This means they're optimized for different workloads. GPT-5.1 is built for complex tasks that require deeper reasoning, while Grok 4.20 offers better value for routine operations.
Output costs matter too. GPT-5.1 charges $10.00/1M output tokens vs $2.50 for Grok 4.20. For generation-heavy workloads (content creation, code generation, summarization), output pricing often dominates your bill. Grok 4.20 has the edge here at $2.50/1M output tokens.
Multimodal capabilities: Both models support vision (image understanding), so you can send images alongside text prompts with either option.
Best Use Cases
Choose GPT-5.1 when:
- • You need more capabilities (audio)
- • You're already using OpenAI's API ecosystem
Choose Grok 4.20 when:
- • You need a larger context window (2,000,000 tokens)
- • You're already using xAI's API ecosystem
Pros and Caveats at a Glance
GPT-5.1
- • Input pricing: $1.25/M tokens
- • Output pricing: $10.00/M tokens
- • Context window: 1,000,000 tokens
- • Max output: 131,072 tokens
Watch out for
- • Higher output cost than Grok 4.20
- • Smaller context window than Grok 4.20
Grok 4.20
- • Input pricing: $1.25/M tokens
- • Output pricing: $2.50/M tokens
- • Context window: 2,000,000 tokens
- • Max output: 131,072 tokens
Watch out for
- • Trade-offs are minor in this matchup.
Try Different Scenarios
Use the calculator below to see how costs change with different usage patterns
GPT-5.1 (OpenAI)
Grok 4.20 (xAI)
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Sign Up for xAI →Frequently Asked Questions
Which is cheaper, GPT-5.1 or Grok 4.20?▼
What is the context window difference between GPT-5.1 and Grok 4.20?▼
Which model is better for AI Agent / Agentic Workflows?▼
Which model has better overall pricing for heavy usage?▼
Where can I compare OpenAI and xAI API pricing beyond this model matchup?▼
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