At What Age Do Dogs Stop Growing? Interesting Development Dacts

A puppy with a football toy.
A puppy with a football toy. Photography ©WilleeCole | Thinkstock.
Last Updated on November 17, 2023 by Dogster Team

My youngest dog, Sirius is an 11-month-old Newfoundland puppy. She is adorably fluffy, huge — and still growing!  It seems like everywhere we go, people stop to ask about how much she weighs. Many of the people we meet are surprised to learn that she’s not her full size yet — even at almost a year old. To answer the question “when do dogs stop growing?” we spoke with Dr. Jerry Klein, the Chief Veterinary Officer for the American Kennel Club, to learn more about the ways dogs grow and the stages of growth for dogs and puppies.

Rate of dog growth

A puppy wagging his tail.
When do dogs stop growing? That depends on a few different factors. Photography ©MirasWonderland | Thinkstock.

Different dogs grow at different rates, based mostly on the size of dog they will be when they reach adulthood. Small dogs grow much quicker than large dogs, and reach maturity at a younger age. “Toy breed dogs may reach full growth as early as 9-10 months of age, while some of the giant breeds of dogs may take up to 18-24 months of age to fully attain their final mass and growth,” Dr. Klein explains.

Dog growth and mental maturity

Small dogs mature quicker mentally, too. “As a rule, smaller breeds mature more quickly than larger or giant breeds,” Dr. Klein says. Since I’m raising a large-breed puppy, this is something that is always on my mind. Even though Sirius is much larger, and nearly twice as old as her best friends (a pair of six-month-old Border Terriers), she is actually significantly less mentally mature than they are.

How puppies develop 

While all puppies develop at different rates, there are a few consistent stages of growth for all puppies. From the day they are born until about three weeks old, puppies are extremely fragile and reliant upon their mothers. At this age, their “eyes remain closed at birth and stay closed until two weeks of age,” explains Dr. Klein.

From three weeks to eight weeks, puppies become much more mobile; engaging with their littermates and the world around them. Between two and three months of age  “a puppy encounters different situations, which could cause apprehension …x Positive reinforcement is needed to prevent future mental anxiety,” cautions Dr. Klein. “From 3 to 6 months of age, puppies start their ‘terrible twos,’ as they are teething, active and challenging. Ages 6 to 12 months can be understood as a puppy’s ‘teenage’ years,  awkward mentally and physically. They are at their most active and playful and, in some breeds, may start to develop sexual maturity.”

Factors that determine how quickly dogs grow

A variety of factors contribute to how quickly dogs grow, and when dogs stop growing. “Genetics certainly are a huge factor, but also environment as well: proper nutrition, health and stimulus, such as exercise/training, even lighting, has been known to affect growth,” explains Dr. Klein.

It’s no surprise that food is high on the list of things that factor into puppy growth — both the quality of the food the puppy is eating and the quantity. While your puppy is growing, be especially attentive to how much you feed him. It sounds counterintuitive, but if you are raising a large-breed puppy, you don’t want to necessarily feed him a lot. “Studies have proven that obesity in puppies, especially in rapidly growing larger breeds, can greatly contribute to the development of hip dysplasia and other orthopedic issues,” Dr. Klein advises.

Caring for a puppy’s growing joints:

Puppies have a lot of energy, but be thoughtful about how much exercise they get, and how strenuous those activities are. Dr. Klein explains that, for example, “there are risks of pushing an extensive, prolonged jogging program on an immature dog as it could cause stress on the joints and growth plates and mean long-term health problems.”

Things like hiking, or more high-impact dog sports like agility or disc dog, should also be approached very cautiously with a growing dog. It’s important to only work on foundation skills that are low impact until your puppy is done growing. Dr. Klein advises to tailor exercise for puppies to the “individual dog, size, age and breed” after consulting with your veterinarian.

Is my puppy done growing? How big will my puppy get?

“The question many dog parents want to know is if their puppy is done growing,” Dr. Klein remarks, before advising that “a good way to know if a dog has stopped growing is when you can no longer feel the ‘knobs’ on their ribs” He also suggests consulting directly with your breeder (if you have a purebred puppy) and/or with your veterinarian to help you determine if your puppy is still growing. Each breed, and each puppy, grows differently.

As puppies grow, their growth plates close, and until that happens, you don’t want your puppy doing any strenuous activity. Many parents of large-breed puppies who intend to train/compete in sports like dog agility, will have x-rays taken of their young adult dogs to confirm if their growth plates have closed. This signifies that it’s safe for the dog to begin jumping and begin learning other more physically demanding skills.

How big will a mixed-breed puppy get? When does a mixed-breed dog stop growing?

Unfortunately, Dr. Klein confirms that there is no way to know for sure how big a mixed-breed puppy will get when he reaches adulthood. “One can try to ‘guestimate’ the future size of a mixed-breed dog if you have an idea of the parents or breeds behind a dog, but unfortunately, there is never a guarantee that you will be 100 percent accurate, as many mixed breed dogs come from a combination of multiple types of dogs,” he says.

I’ve had friends believe they were adopting Chihuahua mixes only to find that they have a large, 60-pound dog a year later! One option to aid in trying to estimate how big your puppy will get is to do a DNA test. While this still can’t guarantee the size of dog your puppy will grow into, knowing what breeds your puppy is a mix of can give you a better idea of what to anticipate in terms of adult size.

Big or small, puppies are a lot of work. It’s key to remain patient and consistent in your training while they are growing. “Raising a puppy is like raising a child,” Dr. Klein says. “They go through the infant stage, [then] the ‘terrible’ stages of chewing and reckless adolescent behavior, until they eventually settle into their own maturity.”

Sassafras Lowrey is an award-winning author. Her novels have been honored by organizations ranging from the Lambda Literary Foundation to the American Library Association. Sassafras is a Certified Trick Dog Trainer, and assists with dog agility classes. Sassafras lives and writes in Brooklyn with her partner, a senior Chihuahua mix, a rescued Shepherd mix and a Newfoundland puppy, along with two bossy cats and a semi-feral kitten. Learn more at

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Featured Image Credit: WilleeCole | Thinkstock. 

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