What this tool does
A CIDR block is an IP address plus a prefix length. This calculator derives the network and broadcast addresses, the usable host range, netmask and wildcard mask. It supports IPv4 prefixes from /0 to /32, including the special /31 and /32 cases.
How to use it
- Enter an IPv4 address with a prefix, such as 192.168.1.10/24.
- Read the network and host range.
- Copy any value you need.
Questions
How are usable hosts calculated?
For /0 to /30 it is 2^(32-prefix) − 2. For /31 both addresses are shown as usable; /32 has one address.
Does it support IPv6?
Not yet. This calculator is intentionally IPv4-only so the output stays unambiguous.
What is the wildcard mask?
The bitwise inverse of the netmask. It is used by ACLs and some routing configuration.