Worked example
192.168.1.42/24 belongs to 192.168.1.0/24 and has usable hosts from 192.168.1.1 through 192.168.1.254.
CIDR / Subnet Calculator
Enter any IPv4 address in CIDR notation to instantly calculate the network address, broadcast, usable range, subnet mask, wildcard mask, and binary breakdown.
Input
What is CIDR notation?
CIDR notation expresses an IP address and routing prefix as a single string, e.g. 192.168.1.0/24. The number after the slash is the prefix length — count of leading 1-bits in the subnet mask.
Wildcard mask
The wildcard mask is the bitwise inverse of the subnet mask. Used in Cisco ACLs, OSPF, and firewall rules. For a /24, the wildcard is 0.0.0.255.
How to use CIDR Calculator
Enter an IPv4 address with a prefix to calculate its normalized network, broadcast, masks, address count, and usable host range.
Common mistake
Do not assume the address entered before the slash is already the network address; host bits may be set.