IP Subnet Calculator
Calculate the network address, broadcast address, mask, and usable host range from a CIDR address.
How to Use the Subnet Calculator
- Enter an IPv4 address with a CIDR prefix, like 192.168.1.10/24.
- The network address, broadcast address, mask, and usable host range appear instantly.
Frequently Asked Questions
What does the /24 in an address like 192.168.1.0/24 mean?
The number after the slash is the CIDR prefix length — it tells you how many of the address's 32 bits are fixed as the network portion. A /24 means the first 24 bits identify the network, leaving the remaining 8 bits for host addresses within it.
Why are only 254 addresses usable in a /24 network, not 256?
Out of the 256 total addresses in a /24, the very first address is reserved as the network address (identifying the subnet itself) and the very last is reserved as the broadcast address (sent to every device on the subnet), leaving 254 addresses that can actually be assigned to devices.
What's different about /31 and /32 networks?
A /32 identifies exactly one single address with no network/broadcast split. A /31, per RFC 3021, is a special case used for point-to-point links where both addresses in the tiny 2-address range are usable, since there's no need for a separate broadcast address between exactly two devices.
Is the IP address I enter sent anywhere?
No — all the subnet math happens entirely in your browser using JavaScript, so nothing you enter is ever sent to a server.