Free CIDR / Subnet Calculator
Enter an IPv4 address and prefix length to get the network address, broadcast address, mask, and usable host range.
| Network address | |
|---|---|
| Broadcast address | |
| Subnet mask | |
| Wildcard mask | |
| Usable host range | |
| Usable hosts | |
| Total addresses |
Frequently Asked Questions
What do /31 and /32 mean for usable hosts?
A /32 is a single host (1 usable address, no separate network/broadcast). A /31 is a special case (RFC 3021) used for point-to-point links — both addresses in the pair are usable, with no dedicated broadcast address. Every other prefix reserves the first address for the network and the last for broadcast.
Does the IP need to be the network's first address?
No — enter any address inside the subnet and the calculator works out the correct network address for you, the same way real network tools do.
What's the difference between subnet mask and wildcard mask?
The subnet mask marks network bits with 1s and host bits with 0s (e.g., 255.255.255.0). The wildcard mask is its exact inverse (0.0.0.255) — used in contexts like Cisco access lists.
Is my data sent anywhere?
No. All calculations happen entirely in your browser. Nothing is transmitted or stored.