When Do Dogs Stop Growing? Puppy Growth Explained

Purebred Boxer little puppy sitting and big dog laying in the grass on sunny summer day. Two pets in spring outdoors.

Dogs come in all shapes and sizes, from tiny Chihuahuas to huge Great Danes and everything in between. And while puppies are undeniably adorable, they seem to grow up so quickly. Going through the puppy stages, they grow rapidly until becoming adults, at which point they no longer increase in size. But when exactly do dogs stop growing? How do we know when a dog is fully grown? And what factors impact how big puppies grow?

 

As it turns out, all dogs stop growing at different rates and reach their full size at different ages. Bigger breeds need longer to reach their full size than small breeds. Here we discuss this in more detail and help you determine how big your puppy will become.

Dog Size Growth Factors

To answer the question “When do dogs stop growing?”, we need to understand the factors that affect size. These can split into environmental factors and genetic factors, which combine to produce a final height. Below we look at some of these factors in more detail and how each impacts the full size of your dog when it reaches maturity:

 

  • Breed: Breed is always the biggest factor that affects the size of your dog when fully grown. A tiny Pug is never going to reach the size of a Dalmatian, or vice versa. Breeds come in all shapes and sizes, so make sure you think hard about what size dog you want when choosing which breed to adopt.

 

  • Gender: In general, fully-grown male dogs are larger than females. This isn’t a hard rule, and there will be some larger females and some smaller males. However, a great way to more accurately guess how big your dog will get is to look at the parents – males usually grow to the same size as the father, while females usually grow to the same size as the mother.

 

  • Nutrition: All puppies need nutrients to grow and develop, and this comes from the food they eat. Dogs that eat well-balanced diets high in vitamins and minerals will be bigger and stronger when fully grown. On the converse, underfed or malnourished dogs will struggle to reach their full size, often lacking muscle and having smaller bones.

 

  •  Genetics: Nutrition and other environmental factors all affect size, but genetics is the largest predetermining factor. All puppies are born with genes that dictate how tall they become which are inherited from both parents. Inherited medical conditions can also negatively impact your dog’s height when an adult.

 

With this knowledge, you can have a rough idea of the size your dog will grow to. Alternatively, you can also use a formula to gauge their final based on the fact that most dogs reach 75% of their final size when they are six months old. Simply measure your puppy’s height at six months of age, multiply this measurement by 100, and then divide this answer by 75. This will give you an approximation of how big your dog will be when it stops growing.

When Do Small Dogs Stop Growing?

As we’ve just established, the breed of dog you choose will dramatically impact how big your dog becomes. Small breeds don’t grow as much, and therefore stop growing at a younger age. Their smaller bones and muscles simply don’t need a long to develop. Common examples include Pomeranians, Cavalier King Charles Spaniels, and Bichon Frise dogs.

 

So, how long do dogs grow if they’re small breeds? In general, most small dogs such as the breeds listed above reach their full size between the age of 6 and 8 months. When they stop growing, they’ll approximately weigh between 22 and 25lbs and stand around 10 inches tall.

When Do Medium Dogs Stop Growing?

If you have a medium-sized breed, the age your dog stops growing is a little later. This is because these breeds have bigger muscles and bones, which need more time to develop. Examples include Poodles, Border Collies, and American Staffordshire Terriers.

 

On average, you can expect your medium dog to reach its full size between the age of 12 and 15 months. The quickest period of growth occurs between 8 and 12 weeks in which medium dogs double their size. The rate of growth then gradually slows. Fully grown dogs will weigh anywhere between 20 and 60lbs depending on the exact breed in question, and height ranges from 8 to 27 inches.

When Do Large Dogs Stop Growing?

When does a dog stop growing if they’re a large breed? Well, as the biggest dogs, it should come as no surprise that these canines take the longest amount of time to reach their full size. Their fully-grown height is much larger than their puppy size, and developing these large and strong bones and muscles requires time.

 

Large dogs such as Labradors and German Shepherds don’t stop growing until they’re around 18 months. Like medium dogs, they grow rapidly between 8 and 12 weeks of age and double their size. However, their rate of growth slows substantially, meaning the total time spent growing is lengthened. When fully grown, they’ll be between 50 and 70lbs and stand between 24 and 44 inches tall.

 

Giant breeds such as the Saint Bernard and the Mastiff take even longer, with full maturity not being reached until around 2 years. However, they will have grown to their full height by around 18 months of age. At this point, your dog will likely look lanky! The next few months are spent “filling out” and gaining weight rather than height. They’ll weigh between 100 and 200lbs when fully grown.

Mixed-Breed Dog Growth

The average size of the dog breed you have is a great determining factor when working out when dogs stop growing. However, accurately guessing when a mixed breed will stop growing is a lot more difficult. These dogs have two sets of genes from different breeds, so it’s hard to predict how these will combine.

 

Generally, it is best to look at the size of the father for male dogs and the size of the mother for female dogs. As mentioned earlier, males and females roughly grow to the same size as their father and mother, respectively. With that said, your dog’s true size is likely to be a combination of the two, so it is difficult to predict their full size accurately even with this knowledge. Things become even more challenging if you are unable to track the mother and father.

 

If you really want to know how big your dog will be when matured, you might consider getting a DNA test. By understanding the genetic profile of the dog, you can gain insights into what height genes they have in their genome and how this will present. Yet remember, this isn’t concrete! Environmental factors also impact height, and there is some variation even within dogs of the same breed.

Final Thoughts

“When does a dog stop growing?” is a question asked by most pet parents. For one, everyone is curious to see the type of dog their playful pup will grow into. But more importantly, you need to check that your puppy is growing at a healthy rate. You want to give your pooch the best start in life and help them grow into a strong and healthy adult.

 

Use this article as a rough guide to see how your dog is growing. And always make sure to check in with your vet if you have any concerns over your dog’s health. Puppyhood is the time for growth and development, and it needs to be monitored carefully.

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