Calcuverter!

Qalculate! is a multi-purpose desktop calculator for GNU/Linux and Windows. It is small and simple to use but with much power and versatility underneath. Features include customizable functions, units, arbitrary precision, plotting, and a user-friendly interface (KDE or GTK+).

The Units program converts quantities expressed in various scales to their equivalents in other scales. The units program can handle multiplicative scale changes as well as nonlinear conversions such as Fahrenheit to Celsius or wire gauge. Units comes with an annotated, extendable database defining over two thousand units.

errProof offers a collection of web-based unique tools for any user

The collection of unit measurement converters along with conversion factor, ratio, formula and tables