IPv4 /21 CIDR Subnet & Usable IP Range Calculator
Compute subnet mask (255.255.248.0), total host addresses (2048), usable hosts (2046), wildcard mask, and network boundaries for /21 subnets.
Formula & Calculation Logic
Usable Hosts = 2^(32 - CIDR) - 2
Inputs used by this tool
Enter values in the interactive controls when the page loads. The result depends on the assumptions and units shown for each field.
Input type: text
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