I have a small cat and a large cat. Mac is about 7 lbs. tops. But he is definitely Alpha Cat in our house. Ming is BIG. That's the only way I can say it, BIG. He is a big-boned cat (odd for a Siamese) and tall. He must weight around 20 lbs., if not more. He is on meds that seem to increase his appetite and his weight. I didn't know that amitriptyline did that, but my vet said it can happen sometimes. It sure did with him. He used to be 14 lbs. Oh well.