This tool asks for 9 measurements. It uses them to figure the important details of the wing and the horizontal tail, which are the important details for working out a CG. It also asks you to make a decision on the Static Margin and suggests how to do that. It figures MAC of both wing and h.tail and the neutral point etc etc etc. All you gotta do is measure what it shows you to measure.

No need to do any figuring, the program does all that.

It uses the formulas that the aeronautics industry has used ever since it figured them out.

http://www.geistware.com/rcmodeling/cg_super_calc.htm