Grok 4.1 Fast vs GPT-5.1: Pricing Comparison
Compare pricing, capabilities, and costs for your LLM workloads.
xAI
Grok 4.1 Fast
Pricing (per 1M tokens)
Input$0.2000
Output$0.5000
Cached Input$0.0500
Context & Output
Context Window2M tokens
Max Output16K tokens
Capabilities
Categorymid
Multimodaltext + image
Fine-tuningNo
StreamingYes
OpenAI
GPT-5.1
Pricing (per 1M tokens)
Input$1.25
Output$10.00
Cached Input$0.1250
Context & Output
Context Window400K tokens
Max Output128K tokens
Capabilities
Categoryflagship
Multimodaltext + image
Fine-tuningNo
StreamingYes
Quick Verdict
Cheaper Input Price
Grok 4.1 Fast
84.0% cheaper
Cheaper Output Price
Grok 4.1 Fast
95.0% cheaper
Larger Context Window
Grok 4.1 Fast
+1.6M tokens
Cost Comparison
Sample workload: 1,000,000 input tokens + 1,000,000 output tokens
Grok 4.1 Fast
$0.7000
$0.2000/1M input + $0.5000/1M output
GPT-5.1
$11.25
$1.25/1M input + $10.00/1M output
Grok 4.1 Fast is 93.8% cheaper for this workload.
Frequently Asked Questions
Which is cheaper, Grok 4.1 Fast or GPT-5.1?
For input tokens, Grok 4.1 Fast is cheaper at $0.2000 per 1M tokens. For output tokens, Grok 4.1 Fast is cheaper at $0.5000 per 1M tokens. The overall cost depends on your workload's input/output ratio.
What is the context window size of Grok 4.1 Fast vs GPT-5.1?
Grok 4.1 Fast has a context window of 2M tokens, while GPT-5.1 has 400K tokens. Grok 4.1 Fast supports a larger context window of 2M tokens, which is beneficial for processing longer documents.
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