IP Subnet Calculator

Convert the /prefix into a 32-bit mask (that many leading 1s). AND the IP with the mask to get the network address; OR the network with the wildcard (inverted mask) to get the broadcast. Usable hosts = 2^(32−prefix) − 2. This calculator does all of that instantly.

A /24 has 256 total addresses and 254 usable hosts (you subtract the network and broadcast addresses). A /25 has 126, a /26 has 62, a /27 has 30, and so on — each extra prefix bit halves the host count.

The network address is the first address in the block (all host bits 0) and names the subnet. The broadcast address is the last (all host bits 1) and reaches every host on the subnet. Neither can be assigned to a device, which is why usable hosts is total minus 2.

A /32 is a single host (one address, used for loopbacks and host routes). A /31 has two addresses used for point-to-point links, where by convention both are usable (no separate network/broadcast). This calculator handles those special cases.

A wildcard mask is the bitwise inverse of the subnet mask (e.g. mask 255.255.255.0 → wildcard 0.0.0.255). It is used in access control lists and routing rules to specify which bits can vary.