About

subnetcalculator is a small toolkit for IPv4 and IPv6 arithmetic: networks, masks, ranges, wildcards, and membership. It is built for people who need the number to be right and the exception to be visible.

There is no account. The calculation runs in the browser. A share link puts the address you chose into the URL, which is described on the privacy page.

The site does not look up DNS, WHOIS, geolocation, or cloud-provider reservations. Those are different jobs, and a generic CIDR result is not labeled as compliant with any cloud vendor.