Question: when is a dog full grown?
Answer: Dog Breed Sizes It's safe to say that small dog breeds (Chihuahuas) have reached their full size by 10 months to 1 year of age. Small-medium dog breeds (Toy Poodles, Beagles, Miniature Schnauzers) will finish growth by about 12-15 months and will have reached their full weight by about 18 months.