DEVELOPER TOOL
IP Subnet Calculator
Calculate network address, broadcast, and usable host range from a CIDR block.
About this tool
Enter an IPv4 address and a CIDR prefix length (like /24) to calculate the subnet mask, network and broadcast addresses, usable host range, and total number of usable hosts — useful for network planning, configuring routers and firewalls, or studying for networking certifications.
Frequently asked questions
- What does the CIDR prefix mean?
- It's the number of leading bits in the 32-bit address used for the network portion — a shorthand for the subnet mask. A /24 means the first 24 bits are the network, leaving 8 bits (256 addresses) for hosts.
- Why do /31 and /32 behave differently?
- A /32 is a single host address with no network/broadcast distinction. A /31 (RFC 3021) is a special case used for point-to-point links, treating both addresses in the pair as usable rather than reserving one for network and one for broadcast.
- What's the difference between network and broadcast address?
- The network address (all host bits zero) identifies the subnet itself and isn't assignable to a device. The broadcast address (all host bits one) is used to send data to every device on the subnet at once — neither is normally usable as a regular host address.