Subnet Calculator

What is a Subnet Calculator?

A Subnet Calculator takes an IPv4 address and a prefix length and computes the network address, broadcast address, netmask, total number of hosts and usable hosts for that subnet. It is used when planning IP ranges, VLANs, subnets in cloud services and container networks.

A worked example

For 192.168.1.0/24 the network address is 192.168.1.0, the broadcast is 192.168.1.255, the netmask is 255.255.255.0, the total number of hosts is 256 and the usable hosts are 254.

Why are usable hosts fewer than total hosts?

The network address and the broadcast address are always reserved and cannot be assigned to a device. A /24 subnet therefore holds 256 addresses but offers 254 usable hosts.

Everything in one view

• Network address and CIDR mask.
• Broadcast address for the subnet.
• Usable host range (network and broadcast excluded).
• Total address count for the block.

Reading CIDR quickly

The /24 in 192.168.1.0/24 means the first 24 bits are fixed, leaving 8 host bits — 256 addresses, 254 usable. Each fewer / bit doubles the block: /23 doubles to 512, /25 halves to 128. The trend is the fastest mental shortcut.