My male Saint Bernard was 23lbs at 10 weeks, could have used at least another 10lbs...per vets advice. Figured out he had a food allergy (corn is our main suspect) at 19 weeks. As of a week ago, at 21 weeks he was 65.4lbs, 27" at the shoulder and 30" around the chest. Our vet says to expect him to be close to 200lbs. We brought him home gaining 2-3lbs a week, as soon as he was dewormed that doubled, jumping to 4-6lbs per week. So its probably safe to guess him at 69-71lbs this week...for a 5 month old puppy.
Wow, that's a big pup lol! Baylee was a big puppy... If I remember correctly, she was around 45lbs at 4 months (i can't remember exactly lol). At 11 months she is 62lbs and has stayed right around there for a while now. I don't think she'll get much bigger, maybe 70lbs when full grown. Baylee is a Rottie mix.