Subnet calculator for IPv4 and IPv6 CIDR
Type an address with a prefix, such as 192.168.1.0/24 or 2001:db8::/32, and get the network, netmask, broadcast, usable host range and size.
What the numbers mean
- The prefix length says how many leading bits are the network. /24 means 24 network bits and 8 host bits, which is 256 addresses.
- In IPv4 the first address of a subnet is the network and the last is the broadcast, so a /24 has 254 usable hosts.
- A /31 has two addresses for a point-to-point link, and a /32 is a single host.
Private ranges
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are private: they are not routed on the public internet and are used inside your own networks.
IPv6 is different
IPv6 networks are huge, so counting hosts is pointless. The usual unit is a /64, the size of one LAN, and providers hand out a /64 or larger. The calculator shows how many /64 subnets a larger prefix contains.