IP Subnet Calculator (CIDR)
Calculate network address, broadcast, subnet mask, wildcard, usable host range and host count for any IPv4 address and CIDR prefix.
How to use
- 1Enter an IP address with a prefix, e.g. 192.168.1.10/24, or pick the prefix separately.
- 2Read the network range, mask and number of usable hosts.
How it's calculated
Network = IP AND mask; broadcast = network OR wildcard. Usable hosts = 2^(32 − prefix) − 2, except /31 (2 hosts, RFC 3021) and /32 (1 host).
Frequently asked questions
How many hosts are in a /24?
256 addresses, of which 254 are usable — the first is the network address and the last is the broadcast.
What is a wildcard mask?
The inverse of the subnet mask (0.0.0.255 for /24). Cisco ACLs and OSPF use it to match address ranges.
Which ranges are private?
10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 (RFC 1918). They're not routed on the public internet.