I purchased a food scale from Walmart. I just put them on the scale they usually just sit there. If not get a small box hit put it on the scale first. Hit the "ON" button it should take care of the tare then put your chin inside.
Use an electronic scale with an option to weigh in grams. It's often easier to put a tub on top like an empty cool whip tub, tare it to "0" and put them inside. They don't like to sit still so patience is a must.