Subnet Calculator

Network and broadcast addresses and the number of hosts from an IP and mask, a mask for a number of hosts, possible masks.

What to find:

the network address and number of hosts from an IP address and mask

the mask from the number of hosts

possible masks from a host IP and network address

Addresses are four numbers from 0 to 255 separated by dots. The mask can be given as the number of ones: /26 or 26.

Test yourself

The IP address and subnet mask calculator finds the network address, broadcast address, host range and number of hosts, picks a mask for a number of computers and solves the exam problem: which masks are possible for a given host IP and network address.

How it works

An IPv4 address is 32 bits written as four numbers from 0 to 255. A mask is 32 bits: first ones (the network part), then zeros (the host part). It is written as an address (255.255.255.192) or as the number of ones (/26).

network address = IP address AND mask

The AND is bitwise. The broadcast address has all host bits set to one. A network has 2^{32 − n} − 2 hosts, where n is the number of ones in the mask: the network and broadcast addresses are not given to computers.

Example. 192.168.10.130 / 255.255.255.192 (/26): network 192.168.10.128, broadcast 192.168.10.191, 2⁶ − 2 = 62 hosts.