IP Subnet Calculator
Calculate subnet details for IPv4 and IPv6 networks. Enter an IP address and CIDR prefix to get the network address, broadcast address, usable host range, total hosts, subnet mask, wildcard mask, and binary representation. Perfect for network engineers, students, and IT professionals.
What Is IP Subnetting?
IP subnetting is the process of dividing a larger IP network into smaller, more manageable subnetworks (subnets). This technique is essential for efficient IP address allocation, network management, and security. By borrowing bits from the host portion of an IP address, you can create multiple subnets within a single network.
This calculator works for both IPv4 (32-bit addresses) and IPv6 (128-bit addresses), providing comprehensive subnet details for any network configuration.
How the Subnet Calculator Works
The calculator uses standard networking formulas:
For IPv4:
Network Address = IP Address & Subnet Mask
Broadcast Address = Network Address | ~Subnet Mask
Usable Hosts = 2(32−CIDR) − 2
For IPv6:
Network Prefix = IP Address & (CIDR mask)
Usable Addresses = 2(128−CIDR) − 2 (for /127 and smaller)
The calculator displays the network address, broadcast address, usable host range, subnet mask, wildcard mask, total hosts, and usable hosts. For IPv6, it also shows the expanded address and address type.
Using the Subnet List Feature
When "Show Subnet List" is enabled, you can divide your network into smaller subnets. Select the "Divide into Subnet Size" option to choose the CIDR prefix of the subnets you want to list. For example, if you have a /24 network and select /28, the calculator will show all 16 subnets of size /28 within the /24 network.
❓ IP Subnet Calculator FAQ
What is a subnet mask?
A subnet mask is a 32-bit number used to divide an IP address into network and host portions. It determines which part of the IP address identifies the network and which part identifies individual hosts.
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation is a compact way of representing a subnet mask. It uses a slash followed by the number of network bits. For example, /24 represents a subnet mask of 255.255.255.0.
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses (e.g., 192.168.1.1) and supports about 4.3 billion addresses. IPv6 uses 128-bit addresses (e.g., 2001:db8::1) and supports 3.4×10³⁸ addresses — vastly more than IPv4.
What is a network address?
The network address is the first address in a subnet. It identifies the subnet itself and cannot be assigned to a host. All host bits are set to 0.
What is a broadcast address?
The broadcast address is the last address in a subnet. It's used to send data to all hosts in the subnet. All host bits are set to 1. IPv6 does not use broadcast addresses.
How many usable hosts are in a subnet?
For IPv4, usable hosts = 2(32−CIDR) − 2 (subtracting network and broadcast addresses). For IPv6, usable addresses = 2(128−CIDR) − 2 (for /127 and smaller prefixes).
What is a wildcard mask?
A wildcard mask is the inverse of a subnet mask. It's used in access control lists (ACLs) to specify which bits to match. For example, the wildcard mask for 255.255.255.0 is 0.0.0.255.
What are the private IPv4 address ranges?
The private IPv4 address ranges are: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These addresses are not routable on the public internet.
What is an IPv6 address type?
IPv6 address types include Global Unicast (2000::/3), Unique Local (fc00::/7), Link-Local (fe80::/10), Multicast (ff00::/8), and Loopback (::1). The calculator identifies the type of the address you enter.
How do I enter an IPv6 address?
You can enter IPv6 addresses in full format (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334) or compressed format (e.g., 2001:db8:85a3::8a2e:370:7334). The calculator expands compressed addresses automatically.
What is the difference between /24 and /25?
A /24 subnet has 256 total addresses (254 usable), while a /25 subnet has 128 total addresses (126 usable). A /25 subnet provides smaller subnets but more of them within a /24 network.
What is subnetting used for?
Subnetting is used to: reduce network congestion by limiting broadcast traffic, improve network security by isolating different departments, optimize IP address allocation, and simplify network management.
What is the difference between a subnet and a VLAN?
A subnet is a logical division of an IP network at Layer 3 (network layer). A VLAN is a logical division of a physical network at Layer 2 (data link layer). Subnets and VLANs are often used together but serve different purposes.
What is the maximum CIDR prefix for IPv6?
The maximum CIDR prefix for IPv6 is /128, which represents a single IPv6 address. The minimum is /1, though /64 is the most commonly used prefix for standard subnets.
How do I calculate the number of subnets?
To calculate the number of subnets, subtract the original CIDR from the new CIDR and raise 2 to that power. For example, subnetting a /24 into /27 gives you 2(27−24) = 8 subnets.
What is the difference between a subnet mask and a wildcard mask?
A subnet mask has 1s in the network portion and 0s in the host portion. A wildcard mask is the inverse — 0s in the network portion and 1s in the host portion. Wildcard masks are used in Cisco ACLs.
Can I use this calculator for network design?
Yes. This calculator is ideal for network design, planning IP address schemes, and verifying subnet configurations. Use the subnet list feature to see all subnets in a network.