What Is an IP Subnet Calculator?
This calculator computes key subnet details — network address, broadcast address, subnet mask, and usable host range — from an IPv4 address and CIDR prefix length, essential for network administration and configuration.
How to Use the IP Subnet Calculator
- Enter an IPv4 address.
- Set the CIDR prefix length (e.g., /24 for a standard Class C-sized network).
- View the full subnet breakdown.
Subnetting Concepts
Worked Example
Subnet mask: 255.255.255.0
Network address: 192.168.1.0
Broadcast address: 192.168.1.255
Usable host range: 192.168.1.1 to 192.168.1.254 (254 usable hosts)
Understanding Your Results
The network address identifies the subnet itself and can't be assigned to a device. The broadcast address is reserved for sending to all devices on the subnet. Everything in between is usable for actual device assignment.
Common CIDR Prefixes Reference
| CIDR | Subnet Mask | Usable Hosts |
|---|---|---|
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /28 | 255.255.255.240 | 14 |
| /30 | 255.255.255.252 | 2 |
Frequently Asked Questions
Classless Inter-Domain Routing notation expresses a subnet mask as a slash followed by the number of network bits (e.g., /24), a compact alternative to writing the full dotted-decimal subnet mask.
The first address in a subnet range, used to identify the subnet itself — it cannot be assigned to an individual device.
The last address in a subnet range, reserved for sending data to all devices on that subnet simultaneously — also not assignable to individual devices.
254 — a /24 has 256 total addresses, minus 2 reserved for the network and broadcast addresses.
They represent the same information in different formats — a subnet mask uses dotted-decimal notation (like 255.255.255.0), while CIDR notation uses a slash and bit count (like /24).