Subnet Calculator
Calculate network, broadcast, usable hosts and address range from IP and mask.
How it works
The calculator accepts an IP address and a subnet mask in CIDR notation (e.g. /24) or dotted-decimal (e.g. 255.255.255.0). It automatically calculates the network address, broadcast, usable host range and total available addresses in the subnet.
Facts about the Subnet Calculator
- CIDR notation represents the mask bit count after a slash (e.g. /24 = 255.255.255.0).
- The network address is the first address in the block and cannot be assigned to a host.
- The broadcast address is the last address in the block and is used for communication with all hosts in the subnet.
- /31 and /32 masks in IPv4 have no usable hosts in the traditional model.
Official references
Consult the official routing and addressing specifications:
- RFC 4632 β Classless Inter-Domain Routing (CIDR): The official CIDR specification.
- IANA β IPv4 Address Space Registry: The official registry of IPv4 address blocks.