I just got my very first dog of my own he is a Boston Terrier. He is 7 weeks old. I was wondering how quick they grown in size. I have seen a boston terrier that is 12 weeks old almost twice his size.
I've seen a wide variety of sizes within the BT realm; in fact, there are three sizes for show judging. The AKC describes them in the breed standard -- "Under 15 pounds; 15 pounds and under 20 pounds; 20 pounds and not to exceed 25 pounds." Add to that the genetics extrapolation and you can have BTs in a large variety of height, length and weight. The breeder of my first BT predicted he would top out at about 16 pounds; he was 25 at 2 years old and was NOT overweight for his size. They are who they are, or they are who they turn out to be. Enjoy your BT, no matter what their final dimensions!