You say sheet size, so I'm guessing sheet metal. If you are talking sections, it should be clear how to figure out the yield.
You could export the flat patterns to AutoCAD/Draftsight and lay them out. Then convert everything to regions, subtract the flats from the stock and calculate the resulting area (of the positive or negative, doesn't matter).
You could create an assembly of the flat patterns and lay them out, do some kind of driven assembly cut into the stock, and calculate the resulting area.
You could create a multi-body part from the flat patterns, do a Boolean subtract from the stock, and have a sensor update you with the remaining area.
You say sheet size, so I'm guessing sheet metal. If you are talking sections, it should be clear how to figure out the yield.