This is the main window of ESBUnitConv Pro where you may select one from the many measurement units from and in which you can convert 

From the Tools menu you can access the Circle Calculator which lets you convert circle units like radius, diameter, circumference or area 

The American Wire Gauges window allows you see the correspondent of american wire gauges units in mm, inches or area square mm or inches 

The Options window lets you set Display options and also Colours, Tool Tips and also Printing and Popup Calculator options