IP Subnet Calculator

IPv4 addresses consist of 32 bits divided into four 8-bit octets. A subnet mask defines which portion of these 32 bits identifies the network and which identifies the host. Using the CIDR (Classless Inter-Domain Routing) notation—such as /24—you specify the number of network bits (e.g., 24 bits for the network, leaving 8 bits for hosts). The network address is found by applying a bitwise AND operation between the IP address and the subnet mask. The broadcast address uses the remaining host bits turned to 1s. Total hosts are calculated as 2^(32 - n) where n is the CIDR prefix, while usable hosts subtract two addresses (the network address and the broadcast address) for routing purposes.

Let us walk through calculating subnet parameters for the IP address 192.168.1.50 with a /26 CIDR notation. First, a /26 prefix means the subnet mask has 26 network bits and 6 host bits, translating to 255.255.255.192 in decimal. Second, the total number of addresses available is 2^(32 - 26) = 2^6 = 64 total addresses. Third, subtracting the network and broadcast addresses leaves us with 64 - 2 = 62 usable hosts. The network address is 192.168.1.0, the first usable host is 192.168.1.1, the last usable host is 192.168.1.62, and the broadcast address is 192.168.1.63.

When planning network topologies, always factor in future growth by choosing a sufficiently large CIDR block rather than boxing yourself into a tight host limit. Pay close attention to the first and last addresses of any subnet, as they are permanently reserved for network identification and broadcasting respectively and cannot be assigned to user devices or servers.