Subnet Calculator
Interactive network designer. Plan and visualize your infrastructure.
Base Network
Columns
| Subnet | IP Range | Useable IPs | Hosts | Actions |
|---|---|---|---|---|
| 192.168.0.0/16 | 192.168.0.0 - 192.168.255.255 | 192.168.0.1 - 192.168.255.254 | 65,534 |
How to use "Divide"
Splits the current network segment into two equal halves. For example, dividing a/24 network results in two/25 subnets. This is the foundation of VLSM (Variable Length Subnet Masking).
How to use "Join"
Joins two sibling subnets back into their parent network. Both subnets in a split must be siblings for them to be joinable. This reverses the division process and restores the larger CIDR block.
About Subnet Calculator
What is Subnetting?
Subnetting is the process of dividing a larger network into smaller, more manageable sub-networks (subnets). Each subnet has its own range of IP addresses. Subnetting improves network performance by reducing broadcast traffic, enhances security by isolating network segments, and allows more efficient use of IP address space.
Why We Built This Tool
Network planning requires calculating subnet boundaries, broadcast addresses, usable host ranges, and CIDR notation. Doing this manually with binary math is tedious and error-prone. This visual subnet calculator lets you interactively divide and join subnets, see address ranges in real-time, and export your network plan.
How to Use It
Enter a network address in CIDR notation (e.g., 10.0.0.0/16) to start. Use the Divide button to split any subnet into two equal halves. Use Join to merge two adjacent subnets back together. The calculator shows the network address, broadcast address, usable host range, and total addresses for each subnet.
CIDR Notation Explained
CIDR (Classless Inter-Domain Routing) notation uses a slash followed by the number of network bits. For example, /24 means 24 bits for the network and 8 bits for hosts, giving 256 addresses (254 usable). A /16 gives 65,536 addresses. Each increment in the prefix length halves the available addresses.
VLSM and Network Design
Variable Length Subnet Masking (VLSM) allows using different subnet sizes for different network segments. A server subnet might need a /28 (14 hosts), while a user subnet might need a /22 (1022 hosts). This calculator helps you visually plan VLSM by dividing subnets to exactly the sizes you need.
Private IP Ranges
RFC 1918 defines three private IP ranges: 10.0.0.0/8 (16M addresses for large enterprises), 172.16.0.0/12 (1M addresses for medium networks), and 192.168.0.0/16 (65K addresses for small networks and home use). These ranges are not routable on the public internet and can be freely used within private networks.