Subnet Calculator

About this calculator

This calculator works out an IPv4 subnet from an IP address and CIDR prefix length: it derives the subnet mask, the network address (IP bitwise-ANDed with the mask), the broadcast address (network address with all host bits set to 1), and the number of usable host addresses (2^(32−prefix) − 2, subtracting the network and broadcast addresses themselves).

Network engineers and system administrators use subnetting constantly when designing IP address plans — carving a larger network into smaller subnets for departments, VLANs, or cloud VPCs, sizing subnets to fit a known number of hosts without wasting address space, and configuring routers and firewalls. Enter an IP address and prefix (like /24) to get the full subnet breakdown.