IPv4 Subnet Calculator

CIDR (Classless Inter-Domain Routing) writes an address and prefix length together, like 192.168.1.0/24. The /24 means the first 24 bits are the network portion and the remaining 8 bits address hosts.

The network address is the first address in the block, with all host bits set to 0, and identifies the subnet itself. The broadcast address is the last address, with all host bits set to 1, and reaches every host on the subnet. Neither is normally assigned to a device.

For a /30 or larger block, the network and broadcast addresses are reserved, so usable hosts equals total addresses minus 2. A /31 has 2 usable addresses for point-to-point links (RFC 3021), and a /32 describes a single host.

A subnet mask marks network bits with 1s, like 255.255.255.0 for a /24. A wildcard mask is its bit-for-bit inverse, like 0.0.0.255, and is used in access control lists and routing rules to match the host bits.

Yes. The math is the same for any IPv4 address, whether it is in a private range such as 10.0.0.0/8 or a public one. The class label (A to E) is the historical classful class based on the first octet.

No. All calculations run locally in your browser using 32-bit integer math, so the addresses you enter never leave your device.