CIDR Calculator
Enter an IP address with prefix length (CIDR notation) to get full network details: address range, broadcast, hosts, wildcard, and more.
Frequently Asked Questions
The network address is the first address of a subnet — all host bits are 0. It identifies the subnet itself and cannot be assigned to a host. The broadcast address is the last address — all host bits are 1. Packets sent to the broadcast address reach all hosts in the subnet.
A /24 has 2⁸ = 256 total addresses. Subtract 2 (network + broadcast) = 254 usable hosts. Formula: 2^(32−prefix) − 2.
The wildcard mask is the bitwise inverse of the subnet mask. It's used in Cisco ACLs and OSPF configurations. For /24 (255.255.255.0), the wildcard mask is 0.0.0.255.
A /30 has 4 addresses, 2 usable — the minimum for a point-to-point link. A /31 (RFC 3021) allows 2 addresses (0 usable hosts in classic sense) for point-to-point. A /32 is a host route (one address).