There is a growth chart somewhere in the YT library. The general rule is double the weight at 12 weeks and maybe add a pound. Not all pups follow the rule. Teddy was 5 pounds at 6 months, and he is now a skinny 8 pounds, 4 oz.
Your pup will likely be smaller.
My boys are brothers, and they were not finished growing until they reached one year of age. They developed muscle their second year.