Calculating Your Puppy's Adult Weight

Updated on May 23, 2019
Dragonrain profile image

I am a lifelong animal lover and have a Bachelors of Science degree in biology.

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.

This article is accurate and true to the best of the author’s knowledge. It is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from a veterinary medical professional. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.


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    • profile image


      6 months ago

      I just got a puppy hes a mut his mom was a German Shepherd, and rottweiler his dad was saint bernard, and bernese mountain dog he's only 7 weeks right now and he's almost 15 lbs so I'm guessing he's gonna be huge

    • profile image

      Craig Cote 

      10 months ago

      Calculating the way the author states puts his adult weight at 130 lbs., the size of a Great Dane instead of the Weimaraner that he is. Calculating the way pet lover suggests puts the adult weight at 87 pounds. Since the sire is between 80-85 pounds and his dam is at 75-80 pounds, the 87 pounds sounds right and so pet lover’s calculation is probably the correct one.

    • profile image

      Chris Gilpin 

      10 months ago

      My pit mix is 15 pounds at 10 weeks im afraid he gonna be huge his name is luke

    • profile image

      Jolene F-M 

      12 months ago

      This is great. Adopted 2 boxer\mix females sisters about 3 months old under weight, nobody could tell us how big they would get or what the mix is

      So calculated from the heavier sister 1st equation got 46.28 2nd equation 31.15

      Smaller sister 1st 43.45 2nd 29.25

      This makes me happy knowing I am going to have a dogs about the size of our late brittany spaniel.

    • profile image

      S. Skaggs 

      19 months ago

      According to this genius equation my 12 week old female Labrador will weigh 130lbs when grown.

    • profile image

      Quanchae Smith 

      19 months ago

      My morkie is 1pound 10oz how much will he weight adult size?

    • profile image

      pet Lover 

      3 years ago


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

    • Dragonrain profile imageAUTHOR


      3 years 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.

    • profile image


      3 years 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.

    • profile image


      6 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.


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