Question: by what age is a dog fully grown?
Answer: Medium-large dog breeds (Collies, Labrador Retrievers, Boxers) are at full growth by about 18 months and at their full weight by about 2 years of age. Giant dog breeds (Great Danes, Mastiffs) may take up to three years to reach their full weight, though they should be fully grown into their paws by about 18 months.