Subnetting is a technique used in corporate networks and home networks to break large networks down into smaller logical components called subnets.
Each time a network is partitioned into subnets, the range of available IP addresses is split in half. Each additional bit you use you distinguish subnets results in the network being split in half. The total number of addresses remains the same, but you achieve logical separation between the subnets.
This is best illustrated by an example: Suppose you have a network 10.0.5.0/24 (this notation is called classless inter-domain routing or CIDR notation) and you would like to separate it into distinct subnets. By increasing the subnet mask from 24 to 25, the effect is that you split the 256 addresses in the original /24 network into two /25 subnets, each with half the addresses, 128.
To learn more about subnets and how you can calculate them yourself, see our article on subnetting.
The online subnet calculator takes an IPv4 address or CIDR block and calculates related information about the IP address and subnet. Use this free online calculator to determine subnet mask, wildcard mask, network address, broadcast address, and assignable hosts.
The calculator shows results in dotted decimal notation and binary notation.
View the results in an editable IP address table or print the subnet details for reference. The subnet calculator has a free API that offers functionality for integrating subnet calculations into your own software projects. The online subnet calculator and its associated API are free to use and are ideal for systems administrators, network administrators, Information Technology specialists, and students.