How long or how heavy a pug is going to get when it becomes an adult is contingent on several factors such as the weight and length of its parents, how much it is fed, the quality of the food it is fed, and the overall care that it is given.
With that said, the pug is one of the largest dogs in the Toy Group breed. Female Pugs usually range around 14-15 lbs and Male Pugs will range around 16-18 lbs. However, pugs can grow to be larger than this due to heavier bone and muscle mass, so some pugs will reach 20+ lbs.