Calculating Your Puppy's Adult Weight

Updated on December 29, 2016

So you've just adopted a new puppy, and would like to get some kind of idea on how big he/she will grow up to be. Is there any way to tell, or at least to guess, how big your little fur ball will be as an adult? Is it okay to buy your dog small sized supplies, such as beds, or should you save some money and opt for the extra large size now? Are there any health issues associated with your pooches future size that you should start researching now? Knowing about how large your dog will grow up to be can be very useful for many reasons. Of course we love our dogs no matter what size they are, but if you'd like a way to estimate how big your puppy will grow to be, then you're in the right place!


These easy calculations can be used to estimate about how large your puppy will be as an adult!

  1. Determine how old your dog is, in weeks, and weigh your puppy.
  2. Now here's where the actual math comes in. The formula is (Growth) = Current weight in pounds / Age in weeks. Adult Weight = (Growth) X 52
  3. So, for example, say you have a 12 week old chihuahua mix who currently weighs 6 pounds. Then you'd first determine his growth. So Current weight divided by age in weeks. 6/12 = 0.5. Then you take that growth number, in this case 0.5, and plug it into the next equation. So in this example, the dogs adult weight is equal to 0.5 X 52, which is 26. So the chihuahua mix in this example will grow to an estimated adult weight of around 26 lbs.

Pretty simple, right? Keep in mind though that this is just a rough estimate. There are many factors that go into determining a dogs growth and size, including things like sex, breed, and health. This calculation estimates your dogs weight as if he/she continues to grow the same average amount throughout puppy hood. Keep in mind that it may not be entirely accurate, due to the fact that many puppies, rather than growing continuously, will have a period of fast growth followed by a period of slower growth until they reach their full adult weight. Also keep in mind that different sized dogs reach their adult size at different ages, and even after they obtain their adult size it's normal for them to continue to gain some weight as they fill out more.

Since these calculations are just estimates and can be inaccurate, it can be helpful to look at more than one when trying to determine your dogs future size. Here is an example of another set of equations used to estimate a puppy's adult size.

  1. If you have a toy or small breed dog, use this equation: (Adult weight in lbs) = Weight in lbs at 6 weeks old X 4
  2. If you have a medium or large sized dog, use this equation: (Adult weight in lbs) = Weight in lbs at 14 weeks X 2.5
  3. If you are unsure whether your dog will be a small, medium, or large adult, you can do both of these calculations for your dog to get a weight range.

Dogs come in all shapes and sizes. It's important to love our dogs, no matter how large or small they grow up to be. But if you'd like a rough estimate on your dogs adult size, these simple calculations should help.


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      pet Lover 14 months ago


      I believe you need to deduct you pet's weeks of age from 52 them apply the formula.

    • Dragonrain profile image

      Dragonrain 18 months ago

      Maybe reread the article. In the example given I said chihuahua MIX, not pure breed chihuahua.

      No, puppies do not grow at a linear rate, a fact that I already addressed in the article above. The calculations given are ways to ESTIMATE how large your puppy will grow. There is no way to know for sure, of course, until your dog is full grown.

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      Lol 18 months ago

      There's no way that this is accurate. After 6 months, the puppy should be at least 60% grown. After that, you cut back on the food given and switch to adult dog food formula. Dogs don't grow at a linear rate. You need to take into consideration breed and litter averages. Also, there's no way that chihuahuas grow up to 26 lbs. I call bs.

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      Court 4 years ago

      I have two labrador/boxer mix female puppies.

      They just turned 16 weeks & weigh approximately 30lbs & 35lbs. According to the equation given, their estimated adult weights are between 62-75lbs.

      The vet estimated between 45-55lbs. at full size, so I honestly hope they do not exceed over 60lbs.