This IP subnet calculator takes an IPv4 address and CIDR prefix (or subnet mask) and returns the network address, broadcast address, usable host range, and the number of hosts. It is the everyday tool for planning networks, configuring routers, and understanding where one subnet ends and the next begins.
How subnetting works
An IPv4 address has 32 bits split into a network part and a host part. The CIDR prefix (the /24 in 192.168.1.0/24) says how many leading bits are the network, leaving the rest for hosts. From that, the calculator derives the subnet mask, the network address (all host bits zero), the broadcast address (all host bits one), and the usable host range in between — the addresses you can actually assign to devices.
The number of hosts is 2 to the power of the host bits, minus two for the network and broadcast addresses. A /24 gives 256 total and 254 usable; a /30 gives just 2 usable, ideal for a point-to-point link. Choosing the right prefix sizes a subnet to its devices without wasting address space.
Why it matters
Subnetting divides a network into manageable, isolated segments — improving security, reducing broadcast traffic, and organising address allocation. Getting the boundaries right prevents overlapping ranges and addresses that silently fail to route. The calculator makes the boundaries explicit so you can plan a clean addressing scheme.
Working out the details of 192.168.1.0/24.
- /24 means 24 network bits, 8 host bits, mask 255.255.255.0.
- Hosts = 2⁸ − 2 = 254 usable.
- Network 192.168.1.0, broadcast 192.168.1.255, usable .1 to .254.
192.168.1.0/24 has 254 usable hosts from .1 to .254, broadcasting on .255.
