At What Age Is a Puppy Full Grown?

Depending on the size and breed of your puppy-child, it could be six months to two years before he or she reaches physical maturity. The playfulness may still linger for some time after, though—so be prepared to keep your shoes and clothes out of reach for at least another two years!

Physical Maturity

As a general rule of thumb, small dogs will reach their maximum size faster than their larger counterparts. They typically reach full physical maturity anywhere between six months to a year old. Even though they reach maturity more rapidly than larger dogs, they seem to live many years longer.

While medium breeds, which weigh anywhere from 15 to 35 pounds, may reach their full length and height by the time they are a year old, they may not reach their full muscle mass until they are about 18 months old.

Large breeds and giant breeds reach their full structural size by 18 months of age, but they will not flesh out completely until they are about three years old. Examples of large breeds would be Doberman Pinschers and German Shepherds, while a Newfoundland is an example of a giant breed.

Sometimes, the paws will tell—especially in larger breeds. You may have noticed that large dogs seem to have ungainly legs and paws that seem much too oversized for their bodies. This is a good sign that your dog is still gaining bulk. In small breeds, the size of the paws is not a good indicator.

If you have a large-breed dog who develops more quickly than the usual eighteen months, you should watch out for bone and joint pain associated with fast growth. They may need to be fed a special diet to help ease their growth spurts, or you can give them supplements to alleviate and prevent joint pain.

Behavioral Maturity

While your dog may look full grown, it’s best not to expect that he or she will act full grown. My terrier, Thisbe, was still eating my shoes at three years of age. She took full advantage of the fact that I was forgetful and lazy about putting my things away! A library book was also destroyed during her “childhood” phase, so I was able to use the “my dog ate it” excuse for the first time in my life.

For large-breed parents, behavioral maturity may only first start to appear at about four to six years of age. Unfortunately, larger breeds destroy shoes, clothes, and furniture so much more efficiently; be prepared to prevent or clean up after these events. Never blame your dog—it is your responsibility as a pet parent to make sure your home is organized in a way that allows your dog the freedom to play.

How to Determine If Your Dog Is an Adult

Your dog’s behavior is the best gauge for determining at what stage he or she is. Smaller breeds will act very hyper and playful, even well beyond 12 months. Larger breeds will move around awkwardly, as their motor skills are still developing. All dogs will always be very excited to see you when you come home, although younger dogs and puppies will bounce and jump around eagerly. As dogs mature, they will act a bit more dignified, even though they will still be eager to greet you at the door.

By Gabrielle Allemeier


Canida: How Long Does It Take for a Dog to Reach Maturity?
Love to Know: How to Tell When a Puppy Is Full Grown?

About the Author
Gabrielle Allemeier volunteers her free time as an animal rescuer and foster pet parent. As an animal lover, she enjoys sharing the knowledge she has gained from her experience with a variety of animals. Along with being an animal lover, Gabrielle is a globetrotter. She lives in Los Angeles, California with her terrier, Thisbe.