I know there is a lot at play but there must be some equasion on hul much coil goes through (x) manetic field produces how much cirrent. I don't wnat to start with bying a lot of rare earth magnets and coils of wire to get to acertain factor.

Ok-you need to start with Gauss' law-the magnet alone will not produce electricty, need a moving coil through the field-this is why the shake flashlights work without batteries by the way-the number of coils, the length of wire, the diameter of the wrap etc are variables that do have a formulae-don't know it off hand-but google should or a good textbook...and if you want a continual, DC voltage you'll need something like a whetstone bridge too

thank you I didn't really think of the flashlight as a starting point. I am building a hydraulic Generator with 1 moving part that withstand many times the curent pressure limits of current models. I need to be able to quantify magnet and coil