WinConverter

Converting basic units is easy enough that you can do it without any type of help. However, some complex items require outside input, whether from the Internet or from specialized apps, such as WinConverter.
This software can help you transform between over 1,400 different units, stacked under nearly 80 categories. If there are any missing units that you need to use, you can easily create them by filling out a simple form.
The vast collection of categories this app provides should cover all your needs. Among these you can find mass, length, time, volume, acceleration, energy, power, temperature, conductivity, resistance, density, angle, flow, illumination, chemical, radiation and volume just to name a few. Custom categories can also be added, if you wish so.
These can be accessed from a drop down-menu in the interface or by swapping between the tabs placed at the bottom of the main frame. The units are listed in the two halves of the window (input and output).
Given the large number of available items, WinConverter further allows you to search for both units and categories. Results are displayed instantly.
WinConverter enables you to modify a few settings. For example, you can sort the units in alphabetical order, have the app run on system startup, choose the result number format and even change the font.
The fact of the matter is that WinConverter is an advanced tool that offers a wide variety of options to its users. The interface is quite simple to use and the intuitive layout should be easy to figure out even by less experienced users.