How Big Can A Dog Get? — Predicting Puppy Growth

If you’re just bringing home a puppy, answering the question “how big can a dog get?” or more precisely, “how big can my puppy get?” shows foresight. Puppies grow really fast and if parents are not prepared, they might find themselves suddenly overwhelmed by their dog’s sudden growth.

By knowing how big your dog can get, as well as factors that contribute to their growth, you can effectively prepare yourself and your dog for his growth needs. Thankfully, there are a number of ways you can estimate just how big your puppy might turn out to be at adulthood.

Here’s a little something to chew on. This video gives an overview of everything we are going to be discussing today concerning how to estimate how big your dog can get.


Tips For Determining How Big A Dog Can Get

1. Look At His Breed And Ancestry

This is about the most straightforward way you can determine how big a dog can get. Simply check out adults of your puppy’s breed and you already have an idea of how big they can get when they reach full maturity.

To get an even more specific idea, look at the dog’s parents. Generally, dogs tend to look quite similar to their parents. Since they take their genetics from mom and pop, you can, naturally, place your bet at the average size between father and mother.

That said, determining how big a purebred dog can get is much easier than determining how a big a mixed breed dog can get. We will get to that in a second, but for now, let’s check out other tips for determining how big a dog can get.


2. Predict Weight From Puppy’s Birth

Your teachers were not wrong when they told you that mathematics is your friend. With some simple math equations, it is possible to find out how big a dog can get simply by tracking their age and weight from the moment they are born as puppies. Note, you must keep track from the very first day.

Now, as a general rule, puppies tend to double their birth weight at 1 week old. From then on, they will begin to increase at a rate of about 5 to 10% daily. This percentage is influenced by a number of factors including genetics and diet.

So, how do you calculate this?

Just add 5 to 10% of their daily weight each day until they are 6 weeks old. At this time, how they will grow will now be determined by their breed.

Or to make things easier, you can just use a puppy adult weight calculator and save yourself the stress.

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Predicting Adult Weight For Small and Toy Breeds

small breed
Image by Spiritze from Pixabay

If your dog is a small breed or a toy breed, determining his adult weight is quite easy. Generally, small and toy breeds keep growing after 6 weeks. However, in comparison to larger breeds, the weight gain isn’t quite significant.

So, to estimate their adult weight, simply double their weight at 6 weeks old twice. 

An illustration: if your puppy was weighing 2 pounds at 6 weeks, you’d double that to get 4 pounds and then double the double to get 8 pounds. Therefore, adult weight is most likely to be around 8 pounds.


Predicting Adult Weight For Medium And Large Dogs

how big can a dog get
Image by Светлана Бердник from Pixabay

Compared to smaller breeds, larger breeds will keep gaining weight at the 5 to 10% rate even after the 6-week mark. In fact, in this period, they tend to grow up faster. So, be prepared for growth spurts of a significant magnitude. To estimate their adult weight and size, you should be looking at how they look at 14 weeks.

For predicting size and weight for medium and large dogs, the equation becomes a bit trickier than the more straightforward small and toy breeds.

So, first, you take their weight at 14 weeks and double it.

Then take that same weight at 14 weeks and halve it.

When you’ve gotten the value for these two steps, add them together. The result is the approximate weight of your medium or large breed at adulthood.

So, let’s say your dog was 18 pounds at 14 weeks.

First step, double. This will give you 36 pounds.

Next, halve the weight at 14 weeks. This will give you 9 pounds.

Add both results together. This will give you 45 pounds.

So, your adult breed is most likely to weigh 45 pounds at full maturity.


What if I Didn’t Keep Track Of My Puppy’s Weight From Birth?

Not many dog owners get to touch or see their puppies from birth. In fact, as a general rule, adoption centers do not allow dog parents pick up a puppy until they have reached a certain age. So, unless you currently have a pregnant dog, chances are high that you won’t be able to track your puppy’s weight from birth.

So, how do you make use of this method?

As we said, mathematics is your friend. It is possible to predict the adult weight and size of a slightly older puppy using a simple math formula.

This math formula would work regardless of your puppy’s breed or size classification. However, the variables in the equation will differ from small to medium to large breeds.

The first step in using this formula, you’d need to calculate the weight of your dog at a specific age depending on your dog’s size classification.

12 weeks for small breeds.

16 weeks for medium breeds.

20 weeks for large breeds.


Predicting Your Dog’s Potential Adult Weight If You Couldn’t Track Your Puppy’s Birth

puppy weight
Image by Karen Arnold from Pixabay

So, you take their weight at the specified age for their size classification and divide it by their age in weeks. After this, multiply the resulting value by 52 (yeah, because there are 52 weeks in a year).

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So, random selection, a medium dog.

First, we will be using his weight at 16 weeks. Let’s say that’s 10 pounds.

So, we divide 10 by 16 to give 0.625.

Next, we multiply 0.625 x 52. This gives us 32.5 pounds.

So, by our calculations, this medium-sized dog might be about 32.5 pounds in weight at full maturity.


Estimating The Adult Size Of A Purebred

If your dog is a purebred, predicting his adult size is pretty easy. Simply look at his parents or if you want to work with standards, you can check out the American Kennel Club’s website. There’s a tool that tells you the average weight and height for dogs of different breeds.

If you’re strictly looking for weight alone, this page of the American Kennel Club’s website has a breed weight chart that you can check out.


Estimating The Adult Size Of A Mixed Breed

For a mixed breed, predicting how big a dog can get becomes a little trickier. If you’re adopting especially, there are so many unknowns and that could make predicting a little difficult. However, here are a few factors you can consider.

  • Check out the pup’s parents if you know them. Especially if the parents are the same breed, you should be able to tell just how large the dog would be.


If, on the other hand, the parents are from different breeds, the size of the bitch would have more influence on how large the pup eventually grows up to be.


  • Doubling the weight of your dog at 4 months or 16 weeks is another method some people use. However, if your pup is a giant breed, make that 5 months or 20 weeks instead.


  • The size of your dog’s paws can also give you an idea of their final size. While this isn’t exactly science, it just makes sense that a dog wouldn’t grow beyond a weight that its paws can support, neither would a small breed require large paws.



Factors That Affect Puppy Growth

There are a number of factors that affect how big a dog can get.

1. Gender

One of these factors is gender. Generally, male dogs are bigger than female dogs. Of course, there are cases where a female dog outweighs a male dog of the same breed. It also depends on the genetics and upbringing of the two dogs in question.

how big can a dog get
Image by SnottyBoggins from Pixabay


2. Desexing

Desexing (neutering and spaying) is also another factor that could contribute to a puppy’s growth. If a dog is spayed or neutered early (before the growth plates close), such a dog would most likely weigh more than its counterparts at adulthood.

The reason for this is that, when desexing occurs, the chemicals that are supposed to tell the bones to stop growing have been interfered with. So, even early in life, such dogs already begin to look taller than their age.

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3. Stunted Growth

There are a number of reasons a dog might experience stunted growth. One of the most common causes though is worm infestation. These worms basically leach off the nutrients your dog consumes for his own growth which leads to malnutrition. So, your dog is deprived of the essential nutrients they need to grow.

(Click here to read our article: how long after heartworm treatment can dog be active?)

So, if you notice that your dog isn’t growing at the rate he is supposed to based on what we’ve learned so far, take him to the vet as soon as possible.

Stunted growth isn’t just that your dog does not reach the expected weight and size, a number of health complications can also arise.

Finally, it’s important to ensure that your puppy’s diet is nutrient-packed so they can achieve their fullest growth potential.

To learn more about puppy nutrition, click here to read our article: how long do you feed a dog puppy food?


When Do Puppies Stop Growing?

Most dogs would have reached full maturity at about two years. However, the specific length of time they spend growing would depend on their kind of breed.

For small breeds, in 6 months, they are mostly done. Larger dogs, on the other hand, might need more time (up to two years) for them to grow up fully.


  • Toy breeds generally take about 10 months to 1 year (e.g. Chis and Yorkshire Terriers).


  • Small to medium dogs take about 12 to 15 months growing and hit their final size at 18 months (e.g. Basenjis and Beagles).


  • Medium and large breeds take 18 months to grow and reach final adult size at 2 years (e.g. Golden Retrievers and Collies).


  • Giant breeds require 18 months to grow fully but reach final adult size at 3 years (e.g. Irish Wolfhounds and Great Danes).

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Is My Puppy Underweight?

thin dog
Image by PublicDomainPictures from Pixabay

If a puppy becomes underweight, it could portend bad things for him, so you must ensure that that doesn’t happen. An underweight dog is usually a malnourished one and you can tell by examining their bodies closely.

Most times, an underweight dog would have his ribs poking through the skin. You’re not supposed to be able to see them just by looking at his side. While he shouldn’t be overweight, there should be a considerable layer of fat that prevents you from seeing the ribs but still allows you to feel them when you press into his side gently.

To plump up your dog so that he is back to a healthy weight, you can switch to a weight-gain dog food. Thankfully, puppy foods are high in calories, higher than adult dog foods

Finally, take your pup to the vet if you think he is underweight. It might be a worm infestation or a health issue. Either way, your vet would be the best person to help with an underweight puppy.

In this video, Julie Fudge Smith is explaining how you can determine if your dog is underweight, overweight, or just right. If you have a hard time determining this, Smith’s method of feeling your dog’s ribcage as illustrated in the visual aid should help.