When Do Dogs Stop Growing?

Dogs have a growth spurt during the earliest stage of their lives as puppies. The bones of some can continue to develop until they're around two years of age, depending on the breed.

Speaking to Newsweek, Dr. Jerry Klein, a veterinarian who is the chief veterinary officer at the American Kennel Club (AKC), said the size of a dog is determined by genetics, which differs by breed.

Larger breeds take longer to reach their full adult size than smaller breeds. "Large and giant breed puppies can continue growing up until 24 months of age," Klein said.

Puppies are technically considered adult dogs when they reach one year of age. They continue to grow in size and height as their bones continue to develop, Klein said.

"The 2019 Canine Life Stage Guidelines," published by the Journal of the American Animal Hospital Association (AAHA), says the puppy stage sees dogs experience "rapid growth."

Klein told Newsweek that a dog reaches its final height once "the growth plates of their bones have stopped producing new tissue and become completely calcified." This indicates the growth plates have "closed," which means they've stopped expanding in length.

"Dogs can still grow in weight and mass past the closing of the growth plates however," he added.

When Do Dogs Stop Growing in Size?

Klein told Newsweek small and toy-sized breeds are fully grown by the time they reach six to eight months of age, while medium breeds tend to finish growing when they're about a year old.

The rapid growth seen during the puppy stage can stop from when they're around six to nine months old, depending on the breed and size of the dog, according to AAHA guidelines.

Klein told Newsweek larger breeds take longer to reach full adult size as they have bigger bones that need more time to grow.

"They can grow until they are 12 to 18 months old. In some cases, very large breeds such as the mastiff may reach their full grown size at 24 months of age."

Klein told Newsweek the growth period for purebred dogs is more definitive as they're known for the predictability of their size as well as coat and temperament. "There will be variances within members of each breed and litter, but generally the breed can certainly help determine final size at adulthood."

But determining the growth rate of "a non-purebred with unknown heritage becomes a guessing game to figure out its adult size," he added.

How Much Exercise Does a Puppy Need?

Klein told Newsweek that while puppies have a lot of energy and need exercise to stay healthy, he warned "excessive, prolonged activity, like jogging, especially on hard surfaces, can be detrimental on the bones and joints of growing puppies especially large and giant breeds of dogs."

Dogs less than 14 to 18 months old should never be jogged, especially large and giant breeds, until their growth plates have fully fused, Klein said.

"A better alternative while they're growing is to walk short distances of a quarter-mile or less on softer surfaces like grass or sand until your dog has finished growing or shorter bursts of variable activity," he advised.

Healthy Dog Weight

Having your dog maintain a healthy weight is important for reducing the chances of injury and disease as well as for having a longer life expectancy, the American Veterinary Medical Association (AVMA) advises.

Excess weight can shave more than two years off your dog's life expectancy, while a healthy weight can reduce the risk of "diabetes, high blood pressure, respiratory disease, kidney disease, and some forms of cancer," the AVMA says.

A healthy weight also cuts down your dog's risk of bone, joint and muscle injuries associated with excess weight, it adds.

The AVMA notes: "Your veterinarian can also teach you to assess your pet's body condition by observing your pet's body shape and feeling certain parts of your pet's body. A healthy weight isn't simply a number on a scale; it's about healthy body composition."

Dog Nutrition

Klein told Newsweek: "The key factor that affects a dog's growth is genetics but environmental factors, such as diet, can contribute to optimal growth."

A dog's nutritional needs varies depending on their size as well as how much energy they burn.

"Activity levels may vary dramatically between pets, and will play an important role in determining caloric intake," the American Society for the Prevention of Cruelty to Animals (ASPCA) explains.

Puppies will need to be weaned off their mother's milk and transitioned into eating normal puppy food. Weaning should begin when they are between three and four weeks old. The weaning process should ideally be completed by when they are around seven to eight weeks old, the ASPCA says.

"Dogs begin to show visible age-related changes at about seven to 12 years of age. There are metabolic, immunologic and body composition changes, too. Some of these may be unavoidable while others can be managed with diet," the ASPCA advises.

Newsweek has contacted the AVMA, the American Animal Hospital Association and the American Canine Association for further comment.