IP Subnet Calculator

A subnet (short for "subnetwork") is a logical subdivision of an IP network. Dividing a network into two or more networks is called subnetting. This process improves network security, performance, and management by isolating traffic.

How IPv4 Addresses Work

An IPv4 address is a 32-bit number that uniquely identifies a network interface on a machine. It is typically written in "dotted-decimal" notation, splitting the 32 bits into four 8-bit octets (e.g., 192.168.1.1).

The Subnet Mask

The subnet mask determines which portion of the IP address represents the network ID and which portion represents the host ID. A subnet mask like 255.255.255.0 means the first 24 bits are dedicated to the network, and the remaining 8 bits are for individual hosts (devices).

This is frequently represented in CIDR (Classless Inter-Domain Routing) notation. Instead of writing out the full dotted decimal mask, we simply append a forward slash and the number of network bits. For example, 192.168.1.1 with a mask of 255.255.255.0 is written as 192.168.1.1/24.

Key Terms

• Network Address: The very first IP in the subnet. It is reserved to identify the segment itself and cannot be assigned to a device.
• Broadcast Address: The very last IP in the subnet. Data sent to this address goes to absolutely every device on the subnet.
• Usable Hosts: Every IP address in between the Network and Broadcast addresses. These are the addresses you can actually assign to servers, computers, or IoT devices. Therefore, the total number of usable hosts is always (Total Addresses - 2).