What Is CIDR?

CIDR (Classless Inter-Domain Routing) expresses IP network ranges using a prefix length.

Example

192.168.1.0/24 means the first 24 bits identify the network portion of the address.

Why CIDR replaced classes

Older classful addressing (Class A, B, C) wasted space. CIDR allows flexible allocation sizes that match real network needs.

Try the calculator

IPLocator's CIDR calculator computes network, broadcast, and host ranges locally in PHP without external APIs.