Subnet Calculator
IPv4 CIDR maths: network, broadcast, mask, host range and count.
Frequently asked questions
What does the subnet calculator compute?
From a CIDR like 192.168.1.0/24 it returns the network and broadcast addresses, netmask and wildcard mask, the usable host range and the total and usable host counts.
What is CIDR notation?
CIDR writes a network as an address plus a prefix length, such as /24, indicating how many leading bits are the network portion. /24 equals a 255.255.255.0 mask.
Why are two addresses not usable?
In most IPv4 subnets the network address and the broadcast address are reserved, so the usable host count is two fewer than the total (except /31 and /32).