Down and Dirty Subnet Calculator

Down and Dirty Subnet Calculator makes IPv4 subnet calculations quick and straightforward. Enter an IP address and prefix to see the network address, usable host range, broadcast address, and adjacent subnets—or convert between CIDR notation and subnet masks without entering an IP. Results update as you type, with copy buttons for individual values or the complete calculation. It works offline, requires no browser permissions, and keeps entered addresses on your device. A practical tool for network planning, troubleshooting, and checking subnet details without opening another website.