I agree that by just looking at the weed you can't tell the weight. With that said, most of the time an eighth would fit into and fill up a cigarette cellophane with a little room at the top to seal it. Therefore, most of the time in my experience, a quarter should fit 2 of these cellophanes. Of course, if the weed is very fluffy or dense this isn't true, but otherwise you could get an idea of how much you have.