The NumericalChameleon is a free, open source, platform-independent and
localized software to convert units of almost anything. It provides a modern
graphical user interface, supports more than 3200 units in 82 categories, and
converts numbers with a precision of up to 1,000 significant figures. All
important physical units of categories are included like length, area,
volume, electricity, magnetism, force, power, energy, pressure, mass,
temperature, velocity, acceleration, radioactivity and time. (in Business and
Productivity)