My Lillie was 1.8 lbs at 8 weeks...she (after spay) weighs 5 1/2 lbs...Bentley was 2.5 lbs at 5 months...he is 11 months old and weighs 4 lbs. I don't think he is going to get much bigger....he is leggy (tall) but tiny boned....little face...ADORABLE!!
you never know how big they are going to get Sadie's Mom was 10 lbs and her Dad was 4 lbs...Sadie (after spay) weighs 6 1/2 lbs
edited to add....the rule of thumb is to triple the 8 week weight or double the 12 week weight and add a pound...this had held true for my furbutts