How to use the CIDR Calculator

Enter an IP address with its prefix length in CIDR notation (e.g., 192.168.1.0/24).
Click Calculate or use a quick preset.
The tool shows network address, broadcast, first and last host, subnet mask, wildcard mask, and host count.

CIDR notation explained

CIDR (Classless Inter-Domain Routing) represents an IP range as a base address followed by a prefix length (/24). The prefix length specifies how many bits are the network part. The remaining bits define the host addresses within the network.

/24 — 256 addresses, 254 usable hosts
/25 — 128 addresses, 126 usable hosts
/16 — 65,536 addresses, 65,534 usable hosts
/8 — 16,777,216 addresses

Network address and broadcast address cannot be assigned to hosts, hence usable hosts = 2^(32−prefix) − 2.