Subnet Calculator - Home Network Admin

What is a subnet?

A subnet (sub-network) splits a larger IP network into smaller, self-contained blocks of addresses. Every device on the same subnet can talk to the others directly; anything outside it has to go through a router (typically your home router's gateway address).

An IPv4 address has two parts: the network portion (shared by every device on the subnet) and the host portion (unique to each device). The subnet mask - or its shorthand, the CIDR prefix like /24 - is what decides where the split happens.

Reading the results

Network address - the first address in the block, used to name the subnet itself. It can't be assigned to a device.
Broadcast address - the last address, used to send to every host at once. Also not assignable.
Usable host range - everything between the network and broadcast addresses. These are the IPs you can hand out to devices.
Wildcard mask - the inverse of the subnet mask, used in access control lists and some routing configurations.

For example, 192.168.1.0/24 gives you 254 usable addresses (192.168.1.1 through 192.168.1.254) - plenty for a typical home network. Need help planning static vs. DHCP ranges? Try the DHCP pool planner, or browse the full CIDR cheat sheet.

Frequently asked questions

What does a subnet calculator do?

It takes an IP address and a prefix length (or subnet mask) and returns the network address, broadcast address, usable host range, total host count, and mask.

How many hosts are in a /24?

A /24 contains 256 addresses, of which 254 are usable for hosts after reserving the network and broadcast addresses.

What is the difference between a /24 and a /25?

A /24 covers 256 addresses. A /25 splits that in half into 128 addresses, giving 126 usable hosts per subnet.