How to Estimate the Size of Puppies as Full Grown Dogs

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Puppies are almost universally considered adorable; that's why there are so many videos and photos of puppies online. But every new puppy will eventually grow up into a full grown dog, and it can be hard to prepare for a dog in your home if you don't know what the puppy's adult weight will be.

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While there are many ways to calculate the eventual full size of your dog, keep in mind that they are all just guidelines, and the actual size your dog becomes could be different from your estimations. Using a dog size calculator online or doing some calculations on your own can at least give you some idea of how big your dog will become.

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How big will my puppy get?

A common question people ask after adopting a puppy is "at what age is a puppy no longer a puppy?" The answer isn't as simple as it may sound though. Some dogs will be full grown adults at only six months of age, while other dogs take up to two years to fully mature. Though the specific ages will vary based on dog breed and even the individual in question, the general rule is that a small breed dog will grow up in less time than a large breed or giant breed dog.

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In other words, 6-month-old Yorkie or chihuahua puppies might have nearly reached their full grown size. But large-breed dogs such as mastiffs may still only weigh a fraction of their full adult weight.

Breed is a good indicator of size

One of the best places to start when trying to learn the eventual size of your dog is with the breed. Guessing a purebred's ultimate size is usually pretty simple; just look up a dog registry site such as shih tzus, Newfoundlands, golden retrievers, or huskies from the American Kennel Club. These will give you information both on the average size of the breed and whether there are large discrepancies between the size of males and females of the breed.

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Guessing what the ultimate size and weight of a mixed breed dog will be can be a bit more of a challenge, but if you know what breed the parents are, you can usually estimate that your dog will be ‌somewhere‌ between the sizes of both parents' breeds. If you are trying to estimate what the size and weight will be of a mutt with unknown or mixed breed parents, you could always submit a sample of your dog's blood for a DNA test to get a better idea of what breeds make up your pup's ancestry.

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Size of parents helps with estimate

If you know the parents of the pup, this can also help to estimate puppy growth and the size of your future adult dog. If they're around the same size, female puppies will usually end up around the size of their mother and male puppies will usually end up closer to the size of the male parent. If the dogs are different sizes, your dog will almost certainly be somewhere between the two. When they're drastically different sizes, this can also make it difficult to tell how big the pup will grow to be.

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If you just have the mother to go by, this can still give you some indication. If she's only 15 pounds, for instance, and your 6-week-old pup is already almost 10 pounds, you can reasonably assume your pup will end up a lot bigger. On the other hand, a 5-pound puppy might be closer to the mom's weight.

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Mathematical calculations can estimate weight

If you don't know the puppy's breed and haven't seen the parents, there are more mathematical ways to guess what a puppy's adult size will be. If you at least know whether your pup is a toy breed like a pug or Havanese, a small breed like a dachshund or Yorkshire terrier, versus a medium breed like a boxer, corgi, or beagle, or a large breed like and Saint Bernards and great Danes , you can use a simple puppy growth chart or puppy weight calculator to find their weight, but you'll need to know its weight at 6 or 14 weeks, respectively. A toy or small breed will grow to be around four times its weight at 6 weeks. For medium to large breeds, like border collies, bulldogs, Rottweilers, and Labrador retrievers, dogs will eventually be around 2.5 times their weight at 14 weeks old.

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In other words, a toy poodle who weighs 2 pounds at 6 weeks old will grow to around 8 pounds (two pounds times four) in adulthood. On the other hand, a 24-pound German Shepherd who is 14-weeks-old will grow to be about 60 pounds (24 pounds times 2.5) eventually.

Online tools use information you have

If you don't know what your small dog's weight was at 6 weeks or the large dog's weight at 14 weeks, you might want to look up an online puppy height and weight calculator or a puppy weight chart. These tools enable you to come up with the most accurate size estimate possible; you can find different calculators based on the information you have. Some will only look at the dog's weight and age, while others will allow you to enter other info for a more accurate answer, which could include whether your dog has been spayed or neutered, gender, and height.

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If you want to do the math yourself, you can also take the current weight of your pup and divide it by the dog's number of weeks of age. With this info you can find out average weight per week and multiply this by 52 (the number of weeks in a year) to find out what the dog could weigh after a year. In other words, if your dog is 10 weeks old and weighs 10 pounds, you would estimate that 10 pounds divided by 10 weeks is one pound per week. After 52 weeks, the dog would weigh around 52 pounds.

This method's accuracy will still vary based on breed size. So for it to be most accurate, you would want to perform this calculation at 12 weeks for a small-breed, 16 weeks for a medium-breed, or 20 weeks for a large breed or giant breed dog.

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Gender, neutering/spaying, and food make a difference

As stated earlier, other factors may affect a dog's growth than simply breed or body weight at a certain age. Dogs that are neutered or spayed at a very young age may not grow as much as those who have the surgery once they reach full size. Gender will often affect a dog's weight, with female dogs usually weighing less than male dogs.

Additionally, these weight estimates are all based on a dog being fed a healthy and age-appropriate diet. Malnourished puppies will grow up to weigh less than expected by genes alone. But even a dog who is fed adequately could have growth issues. In fact, many large dogs can actually have their bones grow too rapidly if they are fed diets with too much protein, calories or calcium. This not only makes dogs larger than they should be, but can also result in bone and joint diseases later in life.

The bottom line

Determining how big puppies will become as adults involves knowing certain factors such as their breed, gender, the breed(s) and size of their parents, whether the puppies have been spayed or neutered, and the dog food they are fed. Mathematical formulas and breed guidelines can help with the process. It is always important to remember, however, that the size of individual dogs may differ from estimations.

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