There's no accurate way to tell a BP's weight without a scale. It'll be smart to invest in a cheap gram scale found in Walmart for like $20-$30. Or if you have a normal scale you can always find out the weight in grams by multiplying the weight by 454. Since there is roughly 454 grams in a pound, it's pretty simple to figure out. So if your BP weighs .73 of a pound, he would be 331 grams. Hope this helps.