IPv4 Subnet & CIDR Calculator

What is CIDR and Subnetting?

Subnetting is the process of dividing a large physical IP network into smaller, logical sub-networks (subnets). Network administrators use subnetting to improve security, reduce network congestion, and allocate IP addresses efficiently across local area networks (LANs).

Understanding CIDR Notation

Classless Inter-Domain Routing (CIDR) replaced the traditional Class A, B, and C networking system in 1993. CIDR uses a prefix suffix (like /24) to specify how many bits in an IPv4 address belong to the network prefix, leaving the remaining bits for host devices.

• /24 (Subnet Mask: 255.255.255.0): Provides 256 total IP addresses, with 254 usable for devices (commonly used in home Wi-Fi networks).
• /16 (Subnet Mask: 255.255.0.0): Provides 65,536 total addresses for enterprise corporate networks.
• /30 (Subnet Mask: 255.255.255.252): Provides 2 usable IP addresses, ideal for point-to-point router links.

Why Usable Hosts Differ From Total IPs

In every IPv4 subnet, two IP addresses are reserved for network infrastructure and cannot be assigned to computers or endpoints:

• Network Address: The very first IP address in the subnet range, used to identify the sub-network itself.
• Broadcast Address: The final IP address in the subnet range, used to transmit data packets to every device on that network simultaneously.

To check your current public network configuration directly, test your setup with our live IP Geolocation Lookup or audit your performance with our Internet Speed Test.