// about this tool

CIDR (Classless Inter-Domain Routing) notation expresses an IP address and its subnet mask as a single string, e.g. 192.168.1.0/24. Given a CIDR block, this calculator derives the network address, broadcast address, first and last usable host, subnet mask, wildcard mask, prefix length, total and usable host count, IP class, address type (private/loopback/link-local/public), and the full binary representation with network and host bits highlighted.

// when to use

Verify that two IP addresses fall in the same subnet before setting up routing
Calculate how many hosts a /27 or /30 subnet can accommodate
Plan VPC or cloud network address ranges before deployment
Understand the binary breakdown of a subnet mask for a networking exam

// faq

What is the difference between network hosts and usable hosts?

In any subnet, the first address is the network address and the last is the broadcast address. Neither can be assigned to a host. So a /24 has 256 total addresses but only 254 usable host addresses.

What does the wildcard mask represent?

The wildcard mask is the bitwise inverse of the subnet mask. It is used in access control lists (ACLs) and OSPF configurations to specify which bits of an address are significant. For a /24 subnet mask (255.255.255.0), the wildcard is 0.0.0.255.

// related tools

// about this tool

// when to use

// faq