IPv4 Subnet Calculator
Get the network address, broadcast address, usable host range, and subnet mask from an IP and CIDR prefix.
| Network address | |
|---|---|
| Broadcast address | |
| Subnet mask | |
| Wildcard mask | |
| First usable host | |
| Last usable host | |
| Total addresses | |
| Usable hosts |
How to use this tool
Enter an IPv4 address and its CIDR prefix (e.g. 192.168.1.10/24) — all subnet details update live.
About this tool
Uses standard bitwise AND/OR/NOT operations on the 32-bit representation of the IP and mask — the same math a router performs — to compute the network and broadcast addresses.
100% client-side. Nothing you type is uploaded, logged, or stored.
Frequently asked questions
What is a /24, /30, etc.?
This is CIDR notation: the number after the slash is how many leading bits of the 32-bit IPv4 address are the network portion. /24 means a 255.255.255.0 mask (256 addresses, 254 usable hosts). /30 means 255.255.255.252 (4 addresses, 2 usable hosts).
Why are only 2 addresses unusable in a subnet?
The first address in a subnet is reserved as the network address (identifies the subnet itself) and the last is reserved as the broadcast address (sends to every host on the subnet), so they can't be assigned to a device. The exception is /31 and /32, which have special handling for point-to-point links and single hosts.