Subnet Calculator
Calculate detailed information about any IPv4 or IPv6 subnet. Enter a CIDR notation below to get the network address, broadcast address, subnet mask, wildcard mask, host range, and binary representations.
How the Subnet Calculator Works
A subnet calculator is an essential tool for network engineers, system administrators, and IT professionals who need to design, manage, or troubleshoot IP networks. By entering a CIDR (Classless Inter-Domain Routing) notation — such as 192.168.1.0/24 — the calculator instantly computes all key properties of that subnet.
The calculator determines the network address (the first address in the block), the broadcast address (the last address used for sending traffic to all hosts), the subnet mask (a 32-bit number that separates the network portion from the host portion), and the wildcard mask (the inverse of the subnet mask, commonly used in access control lists). It also shows the total number of addresses, the number of usable host addresses (total minus network and broadcast), and the first and last usable host IPs.
For IPv6 subnets, the calculator expands the shorthand notation to the full 128-bit address, shows the shortened form, and computes the total number of addresses in the subnet. This is particularly useful for planning large address allocations in modern networks.
Why Use CIDR Notation?
CIDR notation replaces the older class-based addressing system (Class A, B, C) with a more flexible prefix-length format. Instead of rigid /8, /16, or /24 boundaries, you can define subnets at any bit boundary, such as /23, /27, or /30. This flexibility dramatically improves IP address utilization and is fundamental to modern network architecture, including VPC design in AWS, Azure, and Google Cloud.
VLSM and Route Summarisation
Variable-Length Subnet Masking (VLSM) allows you to apply different prefix lengths to different subnets within the same major network, matching each subnet size to actual host requirements. A /30 for a point-to-point link uses only 4 addresses, while a /24 for a branch LAN provides 254 hosts. VLSM is the backbone of efficient IP allocation in modern enterprise networks. Equally important is route summarisation (supernetting), where multiple contiguous subnets are aggregated into a single prefix advertisement, reducing routing table size and improving convergence time across OSPF, EIGRP, or BGP domains.
Use this tool alongside the Supernet Calculator to aggregate multiple subnets, or check for conflicts with the Overlap Detector.