About subnet calculator
Subnetting splits an IP network into smaller ones. The calculator shows the network address, broadcast address, usable host range and subnet mask for any prefix.
Formula
A /24 network has 32 − 24 = 8 host bits, so 2⁸ = 256 addresses, of which 254 are usable for hosts (the network and broadcast addresses are reserved).
Common prefixes
- /24 = 255.255.255.0, 254 hosts.
- /25 = 255.255.255.128, 126 hosts.
- /16 = 255.255.0.0, 65,534 hosts.
- /30 = 255.255.255.252, 2 hosts, used for point-to-point links.
A worked example
To split 192.168.1.0/24 into four equal networks, use /26. Each has 64 addresses and 62 usable hosts: 192.168.1.0–63, 64–127, 128–191 and 192–255. Hosts in different subnets need a router to talk to each other.
Planning tips
Leave room for growth, use a consistent scheme for servers, printers and guest Wi-Fi, and document the plan. Keep guest and office networks in separate subnets for security.
