How Subnetting Works

This IP subnet calculator takes an IPv4 address and a CIDR prefix, builds the subnet mask, and derives the network address, broadcast address, and usable host range. The host bits of the address are zeroed to find the network; the broadcast fills them with ones.

Hosts and Prefix Lengths

Each step shorter in the prefix doubles the address count. A /24 holds 256 addresses with 254 usable hosts; a /16 holds 65,536. Point-to-point links commonly use /30 or /31, wasting nothing.

Private vs Public

RFC 1918 reserves 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for private networks that never route on the public internet. The calculator flags whether your network falls in one of these ranges.