From J. A. Peters and Associates:
Unit Conversion is shareware that converts values from one set of measurements to another. Simple to use, but with advanced features including a molecular weight calculator, the program includes both standalone Windows and MS Excel versions. Behind its simple interface, Unit Conversion includes a flexible parser that allows an infinite number of combinations of units to be evaluated and processed. Unit Conversion allows the user to easily add new units to its database. The fully functional trial version of the program can be installed and used for 30 days (indefinitely for home or non-profit use).