If the Python 3 libraries are not be available for your distribution, this older version can be used with Python 2: rpcalc-0.6.0.tar.gz (36 KB).
Two windows installers are available. Use rpcalc-0.7.1-install-all.exe (7.0 MB) to install for all users (administrator permissions are required). Use rpcalc-0.7.1-install-user.exe (7.0 MB) to install for a single user (administrator rights are not required). The source code for the libraries used to build the Windows binaries is available upon request.