CIDR Calculator
Enter an IPv4 address with a prefix to calculate the subnet, broadcast address, host range, masks and address counts.
What does this CIDR calculator show?
CIDR notation combines an IPv4 address with a prefix length. The prefix tells you how many bits identify the network. For example, /24 corresponds to the subnet mask 255.255.255.0, while /27 provides 32 total addresses.
The calculator determines the network and broadcast addresses, the traditional usable host range, subnet and wildcard masks, and the total number of addresses. Special handling is included for /31 point-to-point links and /32 host routes.
Common examples
A /24 contains 256 addresses, normally 254 usable hosts. A /27 contains 32 addresses, normally 30 usable hosts. A /30 contains four addresses and has traditionally been used for small point-to-point subnets.
Related project
This browser tool was inspired by my offline ESP32 Pocket Admin Toolkit. The source, future article and video can be linked here without changing the calculator itself.