IP Subnet Calculator
Calculate the network address, broadcast address, subnet mask and usable host count for an IPv4 address and CIDR prefix.
About the IP Subnet Calculator
An IPv4 address combined with a CIDR prefix (like /24) defines a subnet: a block of addresses that share the same network portion. This calculator works out the boundaries and usable address range of that subnet.
How it works: The prefix length determines the subnet mask, which is applied to the IP address with a bitwise AND to find the network address; flipping the mask's bits and applying OR finds the broadcast address at the top of the range.
The usable host count subtracts 2 from the total range to exclude the network and broadcast addresses (except for /31 and /32 subnets, which use special rules). This is a core calculation for network engineers configuring routers, firewalls and DHCP scopes.