Layout - Calculating Areas of a Layout object


I was hoping that there is a way to calculate areas of layout shapes rather than just off model faces.
Currently every time I have to create a face in sketchup separate to the model to get area figures as there simply isn’t a face in the model that encompasses the area that i’m after (building floor area etc). It would be far simpler if I can just draw the shape in layout over the view and work the area off of that.