What this site is
Subnet Calculator Free is a small, independent website with free tools for working out IP subnets. You type an IP address and a prefix or mask, and the site shows the network address, broadcast address, wildcard mask and host range. Other pages cover CIDR blocks, IPv6 prefixes, private ranges, IP range conversion, VLSM planning and wildcard masks.
The site is run by a small independent team that builds simple, free tools. It is not a networking vendor, a training company or a certification body, and it is not connected to any router, cloud or software brand.
How the numbers work
Every calculation runs in your browser, and nothing you type is sent to us. One tested script produces every number you see, so the worked examples on the pages and the live tools always agree. Once a page has loaded, the tools keep working without a connection.
We keep the tools plain on purpose. They use the standard rules for IPv4 and IPv6 addressing, treat /31 and /32 networks the way they are used in practice, and reject input that is ambiguous, such as numbers with leading zeros. Results are meant for planning and study. Please check them against your device and provider documentation before you change a production network.
Questions
Found a result that looks wrong, or want a tool added? Use the Contact page.