I write 1, 2, 3, 4, 5 etc. on mine to denote cups. There are 16 in a gallon so I know when I start approaching 10, time to order.
My son made me a label for my 5 gallon deals. 80, 79, 78...LOL!!!
Weighing would probably be better as I bet I forget to cross one off all the time!!
Jim