SIM Converter is an unit conversion program based on the latest standard of International System of Units (SI) and NIST Special Publication 811 (1995 Edition) and provides many more conversions. Licensed under GPL3. Written in C# with Mono & MonoDevelop on Linux.
SIM Converter also runs on Windows with GTK runtime (http://www.go-mono.com/mono-downloads/download.html).
Make sure the SI_factors.xml is in the same folder as the executable.