Subnet Calculator
Calculate network, broadcast, and host information for any subnet.
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Understanding Subnet Calculations
Network Address
The first IP address in a subnet, used to identify the network itself. Hosts cannot be assigned this address as it represents the entire network segment.
Broadcast Address
The last IP address in a subnet, used to send messages to all devices on the network. When a packet is sent to this address, it reaches every host in the subnet.
Subnet Mask
Defines which portion of an IP address represents the network and which represents the host. A mask of /24 means the first 24 bits identify the network.
Wildcard Mask
The inverse of a subnet mask, used in access control lists. Where the subnet mask has 1s, the wildcard has 0s, and vice versa.
Usable Hosts
The number of IP addresses available for devices. Always 2 less than total addresses because network and broadcast addresses are reserved.
CIDR Notation
Classless Inter-Domain Routing notation (e.g., /24) indicates how many bits are used for the network portion. Higher numbers mean smaller subnets with fewer hosts.
💡 Pro Tips
- Plan for Growth: Choose subnet sizes that accommodate future expansion
- Binary Understanding: Learning binary helps understand how subnetting works
- Common Sizes: /24 (254 hosts), /25 (126 hosts), /26 (62 hosts), /30 (2 hosts for point-to-point)
- Private Networks: Use RFC 1918 addresses (10.x.x.x, 172.16-31.x.x, 192.168.x.x) for internal networks