Calculate IP subnets, CIDR notation, network addresses, broadcast addresses, subnet masks, wildcard masks, and the number of usable hosts. This tool runs entirely in your browser — no data is sent to any server.
Subnetting divides a large network into smaller, manageable segments — fundamental to network design and IP address management. Every network engineer needs to calculate subnet boundaries, usable host ranges, and broadcast addresses. This calculator takes an IP address with either a subnet mask (255.255.255.0) or CIDR notation (/24) and computes: network address, broadcast address, first and last usable host IPs, total hosts, and wildcard mask. It's essential for designing network topologies, configuring routers and firewalls, planning IP allocation, troubleshooting connectivity, and passing networking certifications (CCNA, CompTIA Network+).
Dividing a network into smaller segments. A /24 network (256 IPs) can be split into two /25 networks (128 IPs each) or four /26 networks (64 each). This improves security, management, and reduces broadcast traffic.
254 usable hosts. A /24 has 256 total addresses, minus 1 for network address and 1 for broadcast. Formula: 2^(32-prefix) - 2 = usable hosts. /24 = 2^8 - 2 = 254.
The inverse of the subnet mask — used in Cisco ACLs and OSPF configuration. For subnet 255.255.255.0, wildcard is 0.0.0.255. Calculate by subtracting each octet from 255.
They're the same thing — different notations. /24 means 24 bits for the network portion (CIDR notation). 255.255.255.0 is the dotted decimal representation of those 24 bits all set to 1.
The network address (all host bits 0) identifies the subnet itself. The broadcast address (all host bits 1) sends to all hosts on the subnet. Neither can be assigned to a specific device.