Subnet Calculator
Calculate network address, broadcast, IP range, subnet mask, wildcard mask, binary breakdown, and host count from CIDR notation.
What is a Subnet Calculator?
A subnet calculator takes an IP address in CIDR notation (e.g. 192.168.1.0/24) and computes all the key properties of that network: the network address, broadcast address, subnet mask, wildcard mask, usable host range, total host count, IP class, and binary representation. It is an essential tool for network engineers, system administrators, and developers.
Wildcard mask is the inverse of the subnet mask. For /24 (mask 255.255.255.0), the wildcard is 0.0.0.255. It is used in Cisco ACL rules and OSPF area configurations to match IP ranges.
IP Classes: Class A = first octet 1-126 (/8 default), Class B = 128-191 (/16 default), Class C = 192-223 (/24 default). Modern networks use CIDR (classless) routing, but class identification is still useful for understanding address allocation.
How to Use
- Enter an IP address with CIDR prefix (e.g.
192.168.1.0/24) or enter an IP and subnet mask separately. - Click a preset pill for common subnets.
- Click Calculate or press Ctrl+Enter.
- View network details, binary breakdown, and the full CIDR reference table.
When to Use This Tool
Use for network design, IP allocation planning, ACL/firewall rule creation, VLAN setup, and troubleshooting routing issues. Pair with the What's My IP tool to check your public IP details.
Frequently Asked Questions
What is CIDR notation?
CIDR notation expresses an IP address and its network prefix. 192.168.1.0/24 means the first 24 bits are the network, leaving 8 bits for hosts (254 usable).
What is a wildcard mask?
The inverse of the subnet mask. For /24 (255.255.255.0), the wildcard is 0.0.0.255. Used in Cisco ACLs and OSPF to match IP ranges.
How many hosts does a /24 subnet have?
256 total addresses, 254 usable hosts (network and broadcast addresses are reserved).
What is the difference between network and broadcast address?
The network address (first IP) identifies the subnet. The broadcast address (last IP) sends packets to all hosts. Neither can be assigned to a device.
Is my IP data sent to a server?
No. All subnet calculations run entirely in your browser. No data is sent to any server.