How to use this tool
- Enter an IPv4 address, such as 192.168.1.42.
- Enter a prefix length such as 24, or an equivalent contiguous mask such as 255.255.255.0.
- Calculate the network and copy the result. Use CIDR calculator for IPv6 or to test range membership.
Read the result
The prefix counts the bits belonging to the network. For 192.168.1.42/24, the network is 192.168.1.0/24 and the complete address range ends at 192.168.1.255. The ordinary host range is 192.168.1.1 through 192.168.1.254, with 254 conventionally usable addresses.
A subnet mask expresses the same prefix as dotted IPv4. Its one bits must form a continuous run before the zero bits; masks with gaps are rejected. The wildcard mask flips those bits. The binary result helps you see where the network and host portions meet.
Why /31 and /32 are different
An ordinary IPv4 subnet reserves its first address as the network address and its last as broadcast. A /31 can use both addresses on a point-to-point link, so subtracting two would be misleading. A /32 describes one address, often used as a host route.
The calculator shows no broadcast for /31 or /32 and explains the point-to-point convention. This is arithmetic, not a promise that a router, operating system or particular LAN accepts a chosen configuration. Follow the requirements of the equipment and network you manage.
Plan without scanning
The tool computes boundaries and counts locally. It does not discover devices, assign addresses or check for duplicates. Before changing settings, confirm your network's gateway, DHCP range and existing reservations with the router or administrator.
The total address count describes the size of the block, not every address you can safely use in every context. Larger blocks can include special-purpose space, and a correct subnet calculation does not change those reservations.