BaseCalc is a set of programs for converting between any base from 2 to 62. It supports 64 bits of percision and handles fractions. A menu is provided to handle all functions from conversions, program settings and common math operations.
The current version is V1.2 written in May of 1991. You can get the BaseCalc.zip archive here via HTTP with "Load to Disk" set on your Web browser. Yeah, I have not updated it much since it works for for me.