The shih tzu is a compact toy dog breed that has been popular as a companion animal since the days of Imperial China. Shih tzus can come in a number of different colors and markings, but all purebred shih tzus have a distinctive long double coat and reach maturity at a predictable age.
Shih tzu puppies will continue to grow to their full adult height until they are approximately 6 to 8 months in age. However, shih tzus will continue to gain weight until they are approximately 2 years old. At this point, given an appropriate diet that does not lead to obesity or malnourishment, shih tzus will cease to grow larger.
According to the breed standard laid out by the American Kennel Club, full grown shih tzus range from 8 to 11 inches in height at the withers. AKC standard length for this breed is slightly longer than the dog's height, from withers to the base of the tail and the weight is between 9 and 16 pounds.