Subnet Calculator & IP Converter
Work out a network's range from CIDR notation, split it into smaller subnets, and convert addresses between formats. It all runs in your browser.
Subnet / CIDR calculator
IP address converter
About CIDR
CIDR notation writes a network as an address and a prefix length, such as 192.168.1.0/24. The prefix says how many leading bits name the network; the rest name hosts inside it. A /24 leaves 8 host bits, so 256 addresses, of which 254 can be given to devices: the first is the network address and the last is the broadcast address.
A /31 has two usable addresses (used on point-to-point links) and a /32 is a single host. IPv6 works the same way with 128 bits, and its networks are usually /64 or larger, so the totals get very big. The calculator runs in your browser: nothing you type is sent anywhere.