Expand CIDR ranges and compute netmask, host counts and address boundaries — locally.
CIDR / IP Calculator is the network-math companion for scoping. Enter a CIDR block and it gives you the network and broadcast addresses, usable host range, mask and total count.
It runs entirely in your browser, so it is instant and works offline once the page is loaded.
It focuses on IPv4 CIDR math for scoping. For IPv6 planning, use it alongside dedicated subnet tooling.