When Do Dogs Stop Growing in Size?

It's impossible to predict exactly when a dog will stop growing, but here are the most important factors to help you make an educated guess.

By Megan Kriss | Dog Q&A

A guide to when dogs stop growing

Nothing’s cuter than a wiggly puppy, but dogs don’t stay puppies forever. Find out when you can expect your dog to stop growing depending on breed, diet and other considerations.

There are many reasons you might want to know when your puppy is going to stop growing. Maybe you want to know when to switch to adult food or buy your dog’s “final” crate. You may want to start agility training with your dog, but want to know whether his joints are ready. Perhaps you just don’t want the puppy stage to end!

Unfortunately, as with many questions about dogs, the answer is that “it depends.” Let’s take a look at some of the main factors affecting when your dog is likely to reach full size.

The Short Answer

A dog’s growth plates typically close at around nine to eleven months old. When this happens, the dog is unlikely to grow much taller or longer. They may continue to fill out and lose that gangly puppy look, but they are about as big as they’re going to get.

Before this point, a dog’s growth plates are soft and easier to permanently damage. This is why you should be careful not to over-exercise your dog until he’s fully grown and the plates are closed.

It’s important to understand that 9-11 months is the average age. The actual age can vary depending on breed size and other factors. Small dogs, for example, may stop growing in as little as six months, while bigger dogs may continue to grow beyond the year mark.

For a more accurate answer, let’s take a look at some of the primary factors affecting how long a puppy continues to grow.

The Long Answer

A collection of dog breed sizes

Breed Size

Your dog’s breed is probably the best predictor of when they’ll finishing growing.

Generally speaking, the smaller the dog breed, the earlier the dog will reach maturity. That’s not too surprising: a 5lbs adult Chihuahua has a lot less growing to do than a 200lbs Mastiff.

  • Small breeds, like the Dachshund and Corgi, reach their full size between eight and 12 months, but may do so sooner.
  • Medium-sized breeds, like the Collie, stop growing within the eight to 12 month range.
  • Large breeds (breeds that reach 50 to 100 pounds in adulthood) generally finish growing between 10 and 16 months, but may continue filling out longer.
  • Finally, giant breeds usually stop growing around 10 to 16 months, like large breeds, but some continue to grow until they’re 18 months or even older.

As an article in the Journal of Nutrition mentions, this difference in growing ages doesn’t just affect the ultimate size, but also when a dog should be fed as an adult:

“Although a toy or small-breed dog may be considered an adult (and fed accordingly) from ∼9 mo of age, adulthood in the largest breeds is not achieved until ∼15 mo of age.”

For this reason, discuss switching to adult food with a vet, as they have experience judging the growth of a wide range of breeds.

Mixed Breeds

53 percent of pet dogs in the United States are mixed breeds, which makes using breed size to predict when your dog will stop growing even more complicated.

If you know which breeds make up your mutt, the average size can help predict when your puppy will stop growing. But there’s no way to know for sure, unless you’re willing to pay for a DNA test, especially since many mixed breeds have unclear ancestry.

Nutrition

Puppy owners are often concerned about how diet affects growth – and for good reason. Puppies need a nutritionally balanced diet to avoid stunted growth.

Specially formulated puppy food is the best option to provide this, but it’s not essential. As long as your puppy is getting enough vital nutrients and minerals, slightly underfeeding or switching to adult food a bit too soon isn’t going to severely affect growth.

In fact, it’s more dangerous to over-feed, as this can cause obesity and damage developing joints.

Note: You shouldn’t switch to adult food based on size. This decision is dependent on the dog’s age and whether it has stopped growing, which is why it’s best to consult your vet.

Worm Infestation

Intestinal worms, like hookworms and roundworms, can cause a delay in growth if the infestation is severe enough.

These parasites are common in the US and aren’t exclusive to neglected or yard dogs. All pet owners should keep an eye out for signs like an unhealthy coat, diarrhea, a bulging tummy, and a small build despite a huge appetite – although worms may cause no visible symptoms.

Fortunately, once worm treatment has been completed, your puppy’s body will resume normal growth.

Spaying & Neutering

Many people think an early spay or neuter stops a puppy’s growth early due to differences in hormone production. In reality, the age of spaying and neutering usually doesn’t have a big effect on growth.

There is some evidence that early alteration (before 16 weeks) can delay the closure of growth plates, however, causing the dog to grow for longer than they otherwise would. This height difference may not be obvious, but can potentially cause joint problems later in life.

With that said, this is far earlier than most dogs are recommended to be spayed or neutered. Female dogs can usually be spayed from around six months old, while male dogs are usually neutered from 6-7 months. There are exceptions in certain medical circumstances, however, so you should follow your vet’s advice.

Other Considerations

There are a few other things to keep in mind when trying to determine a timeline for your dog’s growth.

Individual Genetics

Each dog is different and there’s natural variation in growth from dog to dog, even when all other factors are the same. Dogs within the same family often show similar growth rates, but one littermate may finish growth much earlier than another.

Unfortunately, there’s no way for pet owners to factor in their dog’s particular DNA when trying to guess when they’ll stop growing. This is simply a random factor that can’t be predicted (yet).

Full Grown Puppies

Finishing physical growth isn’t the only indicator that your puppy has become an adult dog. The adolescent phase usually lasts between 6-18 months, and many dogs retain “puppy-like” behaviour long after this point.

Interestingly, small dogs aren’t just quicker to reach full size, they also reach mental maturity faster than bigger dogs. For this reason, expect medium and large breeds to act like a puppy for longer.

How to Tell If Your Dog Is Done Growing

One way to tell if your puppy is still growing is to feel their ribs. If you can feel the “knobs,” then your puppy is probably still growing, but if not then they’re probably about as big as they’ll get.

While this method is useful, it shouldn’t be used as a basis for decisions that can affect your dog’s health. Instead, consult with your veterinarian for advice about when your puppy has stopped growing.

Summary

It can be difficult to guess when a dog is likely to stop growing. While most dogs reach full size at around 9-11 months old, this depends on a variety of factors, such as breed size, diet, health and genetics.

Do you have any questions about when dogs stop growing? Let me know in the comments!

About the Author

Megan Kriss has been a writer and editor for about five years and a lover of dogs for her whole life. She lives in Georgia with her Border Collie and Chow Chow mix, Ginger, her two cats, Pepper and Misha, and her fiance, Matthew.