Subnet/CIDR Calculator
Calculate network address, broadcast address, usable hosts and more from any IP/CIDR input.
How it works
This calculator takes an IP address in CIDR notation (e.g. 10.0.0.0/16) and
performs bitwise operations to determine the network boundaries. The CIDR prefix length
defines how many bits of the address are used for the network portion — the remaining
bits identify hosts within that network.
Key terms
- Network Address
- The first address in the subnet, identifying the network itself. Not assignable to a host.
- Broadcast Address
- The last address in the subnet, used to send packets to all hosts on the network. Not assignable to a host.
- Subnet Mask
- A 32-bit mask that separates the network portion from the host portion of an address. For example, /24 produces 255.255.255.0.
- Wildcard Mask
- The inverse of the subnet mask. Used in ACLs and OSPF configurations. A /24 wildcard is 0.0.0.255.
- Usable Hosts
- Total addresses minus the network and broadcast addresses. A /24 has 256 total addresses but 254 usable hosts. Exception: /31 networks (RFC 3021) use both addresses for point-to-point links.