About the Subnet / CIDR Calculator
A free tool for finding subnet details from an IPv4 address and CIDR prefix.
What it is
This calculator takes an IPv4 address and CIDR prefix length, and derives the subnet mask, network address, broadcast address, usable host range, and usable host count โ everything needed for basic subnetting.
Features
Full subnet breakdown
Mask, network, broadcast, and usable range in one place.
Any prefix, 0-32
Handles standard subnets plus special /31 and /32 cases.
Input validation
Clear errors for invalid IPs or prefixes.
Instant, private
Runs entirely in your browser. No data is sent anywhere.