What is in your subnet?

Enter an IPv4 address and a prefix length to find the network boundaries, subnet mask and address range.

IPv4 subnet calculator

Calculations run on your device. The addresses you enter are not sent to the server.

Understanding CIDR

The notation 192.168.1.42/24 gives an address and the number of bits reserved for the network. IPv4 has 32 bits in total: a longer prefix means fewer addresses in the subnet.

Prefix	Subnet mask	Total addresses
/16	255.255.0.0	65 536
/24	255.255.255.0	256
/28	255.255.255.240	16
/30	255.255.255.252	4
/31	255.255.255.254	2
/32	255.255.255.255	1

In conventional subnets, the first address identifies the network and the last is used for broadcast traffic. A /31 prefix allows both addresses on a point-to-point link; /32 identifies a single address.

Private addresses

The ranges 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16 are reserved for private networks. Having one of these addresses does not, by itself, make a device reachable from the internet.