IP subnet calculator
Enter an address with a mask in CIDR notation (192.168.1.10/24) or with a four-octet mask (192.168.1.10/255.255.255.0). Without a mask the address is treated as a single host (/32).
What the calculator computes
The mask divides the address space into subnets: the bits on the left (the ones set in the mask) define the network number, the bits on the right are host numbers. The calculator shows the network address, the broadcast address (the last in the subnet), the usable host range and the host count, including the special cases: /31 (two point-to-point addresses per RFC 3021) and /32 (a single address). It also determines the address class and its scope — private (RFC 1918), loopback, link-local or public.