networkDifficulty: 3/5
CIDR Calculator
Enter a CIDR block such as 192.168.1.0/24 to get the network and broadcast addresses, masks, usable host range and host count — including correct /31 and /32 behaviour.
Format: address/prefix
How it works
- Enter a CIDR block such as 192.168.1.0/24 or 10.0.0.0/8.
- Press Calculate to see the network, broadcast, masks and usable host range.
- Host addresses are also accepted — the true network address is shown.
Frequently Asked Questions
How do you handle /31 and /32?
A /32 is a single host route with one usable address. A /31 follows RFC 3021: both addresses are assignable to a point-to-point link, so it reports 2 usable hosts rather than the textbook 0.
What is a wildcard mask?
The bitwise inverse of the subnet mask. Cisco ACLs use it, so it is shown alongside the standard mask.
What if I enter a host address instead of a network address?
The block is calculated anyway and the true network address is shown, so you can see which network the host belongs to.