copper PCB etch for low value resistance:how to get value?

I would use a copper PCB etch for a low value resistance. The resistance will not be a simple stretched trace but will have some bends in order to optimize the available space on the PCB board. I downloaded some tutorials and design notes of TI where is explained how to get the value of a copper PCB stretched trace used as a resistance. The problem comes about the bends, where equations are not completely respected, thus I was looking for a technique in order to computing by my self the value of the total resistance. I was thinking in the FEM (finite element method) but actually I find some difficulties in understanding which kind of equations should be taken into account in this case.
If anyone have some idea, please help me...
Thx a lot.

N.