How Big Will Your Dog Get? A Guide to Estimating Adult Size

When you bring home a puppy, knowing how large they will be as an adult is crucial information. You have to choose puppy food for them — but are they a small breed or a large breed? Feeding giant-breed dogs too many calories at a young age can cause lasting harm to their joints. But if you don’t know your puppy’s breed, then what do you do? 

Which size toys does your puppy need? If you get them a variety now, can you expect them to grow out of that size quickly? Could the toys become a choking hazard?

How about purchasing a kennel? If you get them a size above their needs now, is that enough? Or will you have to buy two kennels? What about their food bowls? How much water should they be drinking? How will you know if they’re eating enough? Most dog-food bags recommend feeding based on the ideal adult weight of that dog, but that means you need to know how big they’ll get.

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When will my dog stop growing?

For all but giant breed dogs, you will have a general idea of a puppy’s adult size by the time they’re six months old. Estimating size can be a hard thing to guess accurately, because the answer depends on breed, individual genetics, diet, neuter status, neuter age, sex, and more.

As you might guess, estimating the adult size of a puppy is easiest for purebred dogs, especially if you know the adult size and weight of their parents or even grandparents. For mixed-breed dogs, learning what their breed mix is by consulting a vet or having their DNA tested can be very helpful. 

Most dogs have finished about 80 percent of their growth by the time they’re six months old, but small-breed dogs tend to finish growing sooner than large-breed dogs. In fact, most dogs are their full adult size by the time they’re one year old, but giant breed dogs can grow until they’re about two. Across breeds, most male dogs are larger than their female counterparts.

Samantha Gehrmann / Stocksy/

How can you tell how big a dog will get?

There are a number of factors to consider when estimating a puppy’s adult size. 

Paw size

This is an incredibly inaccurate way to estimate if a dog will be a larger size when they’re older. The idea is that if their paws look comically large for their current body, they will grow into them — and this is a hint that they will be a large dog. 

The problem is that, even among large and giant breeds, there are huge variations in paw size. Sighthound breeds, such as Greyhounds, have narrow, light feet and generally more delicate bone structure, while breeds such as Mastiffs have thick, wide feet. Both breeds may have the same adult height. Meanwhile, breeds in between could be the same weight but have different paw structures. 

If you notice your puppy’s feet are ridiculously big for their body, you shouldn’t dismiss this observation, but don’t read into it too much either.

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Breed

The single most important piece of information to know when estimating a puppy’s adult size is their breed or breed mix. More than anything else, genetics informs a dog’s size, and if you know their breed or breed mix, you likely know (roughly) how big they will be. 

Within breeds, there can be large variations. These include working lines versus show lines of some breeds, or preferences for different conformations (body size and shape) in a breed in different countries. Even with these variations, knowing a dog’s breed should get you a good enough idea to prepare your house for them and set them up with the correct diet. 

Sex

Across dog breeds, male dogs are generally a little larger than female dogs. This is most accurate within a family line. So within a litter, the male puppies are most likely going to grow up to be larger than the female puppies. When you have a litter of mixed-breed dogs, this can be a bit more varied. Certain puppies may be influenced by one breed more than another in their genetics, and that impacts their adult size and weight. 

Genetics

Genetic testing can be extra helpful when you want to know how big a mixed-breed puppy will be. It is even useful for purebred dogs, especially if you don’t have information about their parents. Learning which breeds are predominantly present in a dog’s DNA can help you estimate their future height, weight, dietary needs, recommended neuter age, and more.

Age at spay-neuter

Most dogs, male or female, will have less caloric needs after they have been spayed or neutered. The age at which they are fixed can lead to larger adult weights, so be sure to consult your vet about the right time to have your dog spayed or neutered. 

Dogs neutered before seven months old tend to weigh just below the adult average, while dogs neutered after seven months old tend to weigh just above.

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Diet

Access to proper nutrition is critical for a growing puppy. Dogs who don’t get a balanced diet or enough calories during critical growing periods may end up stunted or smaller than expected. 

Access to excess food can cause a dog to grow too much, too fast. In giant breed dogs, it’s important not to feed a pup based on their current or predicted weight. Instead, you should adjust their eating portions to their breed, because their growth plates can be damaged by excessively rapid growth at a young age. These dogs continue to grow until they’re about two years old, so there’s no rush.

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Calculating your dog’s adult size

For puppies whose background is unclear, the best way to calculate their adult size is to note how much larger their paws seem compared to the rest of their body. This will give you a general idea of whether they’ll be a small to medium versus a large dog. 

But the most accurate time to estimate their adult weight is at about six months old, when most dogs have finished about 80 percent of their growth. If they are a toy breed (which become full size earlier than average) or a giant breed (which become full size later than average), you can usually tell by six months of age that they’re trending towards a certain size bracket. Although less accurate, once your puppy is four months old, you can take their current weight and double it to get a general idea of how big they’ll be. 

Puppy growth chart

Although it is impossible to predict the exact adult weight of every dog, a good goal is to know which size group they will be in. 

Dog breeds are generally broken up into the following size categories:

• Toy breed: Under 11 pounds

• Small breed: 11 to 22 pounds

• Medium breed: 22 to 57 pounds

• Large breed: 57 to 88 pounds

• Giant breed: More than 88 pounds

Knowing which size category your puppy is expected to fall into helps you decide the size of care items they need, which diet to feed them, what their life expectancy might be, and even which health issues they may be most prone to. 

Want to track your own puppy’s growth to see which size category they may be in? Here are some potential growth markers by age for puppies in different size groups. 

Average puppy weight by size category

References

Salt, Carina, et al. “Growth Standard Charts for Monitoring Bodyweight in Dogs of Different Sizes.” PLOS ONE, vol. 12, no. 9, 5 Sept. 2017, p. e0182064, journals.plos.org/plosone/article?id=10.1371/journal.pone.0182064, https://doi.org/10.1371/journal.pone.0182064.