Subnet / CIDR Calculator
Enter an IPv4 address and CIDR prefix to get the full subnet breakdown.
About Subnet / CIDR Calculator
Subnet / CIDR Calculator takes an IPv4 address with a CIDR prefix and breaks the subnet down into every piece a network engineer or backend developer might need: the network and broadcast addresses, the first and last usable host addresses, the total and usable host counts, and the corresponding subnet mask and wildcard mask in dotted-decimal form.
Worked example: enter 192.168.1.10/24 and the calculator returns network 192.168.1.0, broadcast 192.168.1.255, usable range 192.168.1.1 – 192.168.1.254, 256 total addresses and 254 usable hosts, mask 255.255.255.0, and wildcard 0.0.0.255. Change the prefix to /27 and everything regroups into the corresponding 32-address block — useful when you are splitting a parent allocation into smaller subnets without overlapping ranges.
Edge cases are handled the way modern routers handle them. A /31 is treated as an RFC 3021 point-to-point link with two usable hosts and no broadcast, the convention every modern router and IPAM uses for router-to-router links. A /32 is a single host — one address, no network/broadcast distinction. The tool is IPv4 only; IPv6 subnetting follows different rules (no broadcast, prefix lengths from /1 to /128, hexadecimal addresses) and would be a separate tool.
All math runs in your browser. Internal network plans and IP allocations stay on your machine — nothing is uploaded or stored.