Subnet Calculator
Calculate network addresses, broadcast, host ranges, and CIDR notation.
Enter any IPv4 address (e.g., 10.0.0.1 or 172.16.0.0)
What Is Subnetting?
Subnetting is the practice of dividing a larger IP network into smaller, more manageable sub-networks (subnets). Each subnet operates as an independent logical network, which helps reduce broadcast traffic, improve security through network segmentation, and make more efficient use of limited IPv4 address space. Subnetting is a fundamental skill for network administrators, cloud engineers, and anyone designing or troubleshooting IP networks.
Understanding CIDR Notation
CIDR (Classless Inter-Domain Routing) notation is the standard way to express a subnet. It combines an IP address with a prefix length separated by a forward slash — for example, 192.168.1.0/24. The prefix length (the number after the slash) indicates how many bits of the address are used for the network portion. A /24 prefix means the first 24 bits are the network, leaving 8 bits (256 addresses, 254 usable) for hosts. Smaller prefix numbers like /16 create larger networks, while larger numbers like /30 create very small subnets — often used for point-to-point links between routers.
When to Use a Subnet Calculator
A subnet calculator saves time and prevents errors when you need to determine network boundaries, allocate IP ranges, or configure routing rules. Common use cases include planning address space for a new office or data center, setting up VPC subnets in AWS or Azure, configuring firewall rules and access control lists, and verifying that two devices are on the same subnet. Instead of manually converting between binary and decimal or memorizing subnet mask tables, a calculator gives you instant, accurate results — including the network address, broadcast address, first and last usable host, wildcard mask, and total host count.