Puppy Size Calculator

One of the most common questions veterinarians get asked is “how big will my puppy get?” The curiosity is understandable! After all, knowing how large your canine companion will grow can help you prepare for their future needs, such as the size of their crate or the amount of food they’ll need.

Predicting the adult weight of a puppy is not simple, but we’re confident that our tool is the best puppy growth calculator on the internet. It’s based on the latest scientific studies, and takes into account not only the age and current weight of your dog but also their breed - different sizes of dog grow at very different rates. So whether your dog is a pure-breed or a mix, you need look no further!


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How big will my dog get? What the science says

Most dog weight calculators on the internet are extremely simplistic, and don’t account for the differences between breeds. Many even assume a completely linear growth trend during the first year, which - as anyone who’s ever owned a puppy can tell you - is absolutely not the case! We’re confident that ours is the best you’ll be able to find.

Our calculator is based on data from this study by veterinarians at the University of Liverpool and Banfield Pet Hospitals. Age and bodyweight data of over 50,000 healthy young dogs was used to model the different growth trajectories based on breed size, sex, neuter status, and more. Breeds in the drop-down are categorised into six groups which reflect expected adult weight. Support for the giant breeds group is coming soon.

Valid inputs will generate a chart showing the two centile lines between which the puppy falls, based on current age and weight. The red line plots their predicted weight until adulthood. It’s advisable to weigh regularly to confirm the accuracy of this prediction. It’s possible for healthy puppies to cross centile lines upwards or downwards, but this is more likely to occur when there are developmental problems or nutritional issues. Dogs crossing two or more centiles should be carefully assessed.

For puppies of mixed or unknown breed that deviate from the centile lines, it may be necessary to try a larger or smaller breed category in the drop-down. If they are in good body condition and are seem healthy, consider the possibility that their adult weight will differ from what was expected.

What are growth centiles? 📈

Growth centiles are a way of comparing the size of a puppy to other puppies of the same breed and age. They can help determine whether a puppy is growing at a normal rate, or if there may be an issue with their development.

The growth centiles in our chart - 0.4%, 2%, 9%, 25%, 50%, 75%, 91%, 98%, and 99.6% - represent the range of sizes that are considered normal for puppies of a given breed and age. For example, if a 12 week old Border Collie weighs in around the 50th centile on the growth chart, this means that 50% of Border Collies at the same age are smaller than that puppy, and 50% are larger. In other words, they are very much average-sized. If a puppy falls above the 91st percentile, this means that 91% of puppies of the same breed and age are smaller than that puppy.

Remember that the 50th centile is not a target. In reality, any centile line can be considered healthy - what is more important is that a puppy doesn’t cross between centile lines as they grow. Doing so can sometimes indicate underlying illness or poor nutrition. This is why it is critical to weigh your puppy regularly.

Can you predict the weight of a mixed or unknown breed?

If you have a mixed breed puppy, or have a adopted a stray and don’t know its breed, it can be more challenging to predict their adult weight.

Luckily, our calculator doesn’t need to know your dog’s specific breed for it to work! It includes a range of mixed breed categories, which reflect the approximate adult size of the dog. You just need to know which of these groups they fall into. If you’re not sure, take a look at the dog’s parents or speak to your vet.

  • Toy: expected adult weight under 14lbs (6.5kg), e.g. Toy Poodle, Yorkshire Terrier
  • Small: expected adult weight 14-20lbs (6.5-9kg), e.g. Dachshund, Miniature Schnauzer
  • Medium: expected adult weight 20-32lbs (9-15kg), e.g. American Cocker Spaniel, Boston Terrier
  • Large: expected adult weight 32-65lbs (15-30kg), e.g. Australian Shepherd Dog, Siberian Husky
  • Very Large: expected adult weight 65-90lbs (30-40kg), e.g. Labrador, German Shepherd
  • Giant: expected adult weight 90lbs+ (40kg+), e.g. Great Dane - support for giant breeds coming soon!

You may have noticed our calculator doesn’t yet allow weight prediction for giant breeds. This is because the study found striking differences in the growth patterns of dogs with an adult bodyweight of over 40kg, and so breed-specific modelling is required. Watch this space!

What factors affect a puppy’s growth?

There are many factors that can impact how big your dog will grow, including genetics, nutrition, whether they’ve been neutered, and their overall health.

  • 🧬 Genetics: The breed and size of your puppy’s parents are the most significant factor in determining their adult weight. A Great Dane is obviously going to be much larger than a Chihuahua, even if they are raised in the same environment. However, it’s important to note that within a breed - and even within a single litter! - there can be a lot of variation in size. This is why regular weighing of your puppy is one of best steps you can take to predict their adult size.
  • 🍲 Nutrition: Proper nutrition is crucial for a puppy’s growth and development. If your puppy is not getting enough calories or essential nutrients, it can affect their growth rate. Similarly, overfeeding can also be a problem, as it can lead to obesity and other health issues.
  • Neutering: You may have noticed that our calculator does not ask whether a dog has been neutered. The scientific study powering our calculator found that the changes in energy requirements and growth rates due to neutering were small in comparision to normal variation between individual dogs. For this reason, it’s not necessary to account for neutering in our centile charts.

Other factors that can impact a puppy’s growth include overall health, activity level, and any underlying medical conditions. If you’re ever in doubt about your dog’s wellbeing, you should always contact your vet.

How can I accurately weigh my puppy?

One of the best ways to track your puppy’s growth is to weigh them regularly. Most veterinarians recommend weighing your puppy once a week until they are about 6 months old. After that, you can scale back to weighing them every couple of weeks to once a month.

You have several options:

  1. ⚖️ Use a home scale (and some math!): If you have a home scale that is accurate to at least 0.1 lb / 0.05 kg, you can weigh your puppy on it. It’s often difficult to encourage a puppy to stand still without touching them, and touching them can affect the reading. For this reason, a better approach may be to weigh yourself while holding the puppy, then subtract your own weight from the result.
  2. 👩‍⚕️ Visit your vet: Most veterinarians have a scale that is specifically designed for weighing pets. You can make an appointment to bring your puppy in for a weigh-in every few weeks to track their growth. It’s worth remembering that a quick appointment to use the vet scales will usually be free.

Does the smallest puppy in a litter stay the smallest?

It’s a common misconception that the smallest puppy in a litter will stay the smallest as they grow. This is not necessarily true.

It’s not uncommon for the smallest puppy in a litter to catch up and even surpass their littermates in size. This is one reason why trying to predict the weight of a puppy that’s under 12 weeks using our calculator will present a warning that the result may be inaccurate. Weighing puppies regularly before 12 weeks is vital to ensure appropriate weight gain, but it can’t reliably predict their final adult weight.

On the other hand, some small puppies will just stay small. They’ll fall into one of the lower centiles on our chart throughout their first year, be completely healthy, and their small size isn’t anything to worry about. Just focus on providing them with proper nutrition and care to support their growth and development.

Is a dog fully grown at 10 months?

The age at which a dog is considered full grown varies by breed. Smaller breeds tend to reach their adult size faster than larger breeds, with some small breeds reaching their adult size at around 10 months of age.

Larger breeds, on the other hand, may not be fully grown until they are 18-24 months old. A Labrador, for example, will generally reach adult size by 12 months but may continuing ‘filling out’ for another 6 months after that.

Why is my puppy not putting on weight?

If you’re concerned that your puppy is not gaining weight as they should, you should speak to your vet as soon as possible. Many common reasons why a dog isn’t putting on weight can be remedied with the right treatment.

  • Nutrition: As mentioned earlier, proper nutrition is essential for a puppy’s growth and development. If your puppy is not getting enough calories or nutrients, it can affect their weight gain. Make sure you are feeding your puppy a high-quality puppy food that meets their nutritional needs.
  • Medical issues: Certain health conditions, such as parasites or digestive problems, can cause weight loss in puppies.
  • Stress: Stress can affect appetite and weight gain in puppies. If your puppy is experiencing stress due to changes in their environment or routine, they may not be eating as much as they should.
  • Age: Puppies have different growth rates throughout their first year. They experience rapid growth earlier in life, followed by a gradual drop-off in the rate of growth. Regularly weighing your puppy and consulting a growth chart can help flag up potential problems early on. Consult with a veterinarian if you have any concerns about your puppy’s weight gain.

To summarise: predicting a puppy’s adult weight can be challenging. It depends on a combination of genetics and environmental factors, and growth rates vary dramatically between different breeds. But by using our calculator, weighing your puppy regularly, and consulting with your vet if you’re ever concerned, you can be confident that your puppy is on a healthy growth trajectory.

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