IP Subnet Calculator: Read a CIDR Address at a Glance
CIDR notation hides the whole shape of a network in two digits after a slash. This calculator draws that shape out.
What is the IP Subnet Calculator?
A CIDR address packs a host address and a network size into one short string, and this calculator unpacks it. From an address such as 192.168.1.10/24 it derives the network address, the broadcast address, the first and last usable hosts, and the count of usable hosts. The maths runs entirely in your browser, so no address you check is sent anywhere.
How to use it
- Enter an IPv4 address followed by a slash and a prefix, such as /24.
- Check the prefix matches the network you mean.
- Click Calculate Subnet.
- Read off the network, broadcast, and usable host range.
Worked example
Calculating 192.168.1.10/24 gives network 192.168.1.0, broadcast 192.168.1.255, and 254 hosts.
What network is 192.168.1.10/24 on?
It is on 192.168.1.0, with broadcast 192.168.1.255 and 254 usable hosts from 192.168.1.1 to 192.168.1.254.
Frequently asked questions
Why does a /24 network have 254 usable hosts?
A /24 leaves 8 host bits, giving 256 addresses, minus the network address itself and the broadcast address.
What about /31 and /32?
Those prefixes leave no ordinary usable range, so the calculator reports zero usable hosts for them.