CIDR to IP Range Generator

CIDR (Classless Inter-Domain Routing) notation is a compact way to represent an IP address and its associated network mask. Written as an IP address followed by a slash and prefix length — for example 192.168.1.0/24. The /24 means the first 24 bits are the network portion, leaving 8 bits for host addresses — giving 256 total addresses and 254 usable hosts.

To calculate an IP range from CIDR: (1) Convert the IP to binary. (2) Apply the subnet mask based on the prefix length. (3) The network address is the IP with all host bits set to 0. (4) The broadcast address is the IP with all host bits set to 1. (5) Usable hosts are all addresses between network and broadcast. This tool does all of this automatically.

A /24 CIDR block has 256 total addresses (254 usable hosts) with subnet mask 255.255.255.0. A /16 CIDR block has 65,536 total addresses (65,534 usable hosts) with subnet mask 255.255.0.0. The smaller the prefix number, the larger the network and the more IP addresses it contains.

A subnet mask is a 32-bit number that divides an IP address into a network portion and a host portion. For /24, the mask is 255.255.255.0 — meaning the first 3 octets identify the network and the last octet identifies the host. Subnet masks are used by routers to determine which part of an IP address refers to the network.

A wildcard mask is the inverse of the subnet mask. Where the subnet mask has 1s in the network portion, the wildcard has 0s, and vice versa. For /24, the subnet mask is 255.255.255.0 and the wildcard mask is 0.0.0.255. Wildcard masks are commonly used in Cisco ACLs and OSPF configurations.