GNU Units
https://www.gnu.org/software/units/
http://ftp.gnu.org/gnu/units/windows/
Java
http://sourceforge.net/projects/jconvert/
Python
https://pint.readthedocs.org/en/0.6/tutorial.html
Wikipedia
https://en.wikipedia.org/wiki/Metric_prefix
Other links
http://ptec107.wikispaces.com/file/view/conversion_factors.pdf