IP Subnet Calculator

Break down an IPv4 address and CIDR prefix into its network address, broadcast address, subnet mask, and usable host range.

Subnetting splits a larger network into smaller, self-contained segments. The CIDR prefix (the "/24" in 192.168.1.0/24) tells you how many of the address's 32 bits are fixed for the network portion — the remaining bits are available for host addresses. A /24 leaves 8 bits for hosts (256 addresses), while a /30 leaves only 2 bits (4 addresses), which is why smaller prefixes describe bigger networks and larger prefixes describe smaller ones. The first address in a subnet is always reserved as the network address and the last as the broadcast address, so usable hosts is always 2 less than the total address count (except for /31 and /32, which are special cases).