What this tool does
Enter any IPv4 address and CIDR prefix to instantly get the network address, broadcast address, subnet mask, and the full usable host range — the same math you'd otherwise do by hand or in a spreadsheet during VLAN planning or firewall rule design.
How subnetting works
An IPv4 address is 32 bits, split into a network portion and a host portion by the CIDR prefix (the /24, /27, etc.). Every address in a subnet shares the same network portion; the host portion is what varies between individual devices. A /24 has 8 host bits (256 total addresses), a /27 has 5 host bits (32 total addresses), and each additional prefix bit halves the subnet size.
When you'd use this
Designing a new VLAN, sizing a DHCP scope, checking whether two subnets overlap before a merger or site migration, or working out how many usable IPs a given prefix actually gives you before requesting address space from your network team.
Reading the results
The network address identifies the subnet itself and can't be assigned to a device. The broadcast address is reserved for sending to every host on the subnet at once. Everything in between — the usable host range — is what you can actually assign to routers, servers, and clients.