Subnet Calculator
BetaThis tool is in beta. Some features may change or have limited functionality.Calculate IPv4 subnet details including network address, broadcast address, subnet mask, wildcard mask, usable host range, and total hosts from CIDR notation.
Quick CIDR Prefixes
Subnet Details
Why Use Subnet Calculator?
Subnet calculation is essential for network planning and IP address management. Whether you're designing a corporate network, configuring firewall rules, or setting up VLANs, understanding subnet boundaries helps you allocate IP addresses efficiently and prevent routing issues.
This tool instantly computes all subnet details from CIDR notation, saving you from manual binary math. System architects, network engineers, and DevOps professionals use subnet calculators daily to plan network segmentation, estimate capacity, and troubleshoot connectivity problems.
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation represents an IP address and its subnet mask in the format IP/prefix. For example, 192.168.1.0/24 means the first 24 bits are the network portion, giving a subnet mask of 255.255.255.0 with 256 total addresses.
What is the difference between network and broadcast address?
The network address is the first address in a subnet (all host bits set to 0) and identifies the subnet itself. The broadcast address is the last address (all host bits set to 1) and is used to send packets to all hosts on the subnet. Neither can be assigned to a device.
Why are there fewer usable hosts than total hosts?
In most subnets, the first address (network address) and last address (broadcast address) are reserved and cannot be assigned to hosts. So a /24 subnet has 256 total addresses but only 254 usable host addresses. Exceptions are /31 (point-to-point links) and /32 (single host).
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask. Where the subnet mask has 1s, the wildcard has 0s, and vice versa. It's commonly used in access control lists (ACLs) on Cisco routers and OSPF configurations to define which bits of an address should be matched.
How do I choose the right subnet size?
Choose based on the number of hosts you need. A /24 gives 254 usable hosts, /25 gives 126, /26 gives 62, and so on. Always plan for growth — it's easier to allocate a slightly larger subnet upfront than to renumber later. For point-to-point links between routers, /30 or /31 is standard.