Given an IPv4 address and a CIDR prefix, this calculator works out the network address, broadcast address, subnet mask, the range of usable host addresses and the total host count — instantly and locally.
How to use it
- Enter an IP address (e.g. 192.168.1.10).
- Enter the CIDR prefix (e.g. 24).
- All subnet details are calculated instantly.
- Use them to plan or verify your network.
About IP Subnet Calculator
Subnetting is fundamental to networking but easy to get wrong under pressure. Whether you are carving up an address space, configuring a firewall rule, or sizing a DHCP range, you need to know exactly which addresses a subnet covers and how many hosts it allows. Doing the binary math by hand is slow and error-prone. This calculator derives every value from the IP and prefix the moment you type, so you can confirm a subnet at a glance. All computation runs in your browser.
FAQ
What does the CIDR number mean?
It is how many bits of the address are the network portion. /24 means the first 24 bits are the network, leaving 8 bits (256 addresses) for hosts.
Why is the usable host count two less than the total?
The network address and the broadcast address are reserved, so they cannot be assigned to hosts.
What does CIDR notation like /24 mean?
The number after the slash is how many leading bits are fixed as the network portion. A /24 fixes 24 bits, leaving 8 bits for hosts — that is 256 addresses (254 usable). Smaller numbers mean larger networks.