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Blog /Predicting Puppy Size Potential
Breed and Genetics April 22, 2021

3 ways to predict how big your puppy will get

Wondering whether your dog will grow up to be purse-portable or pony-sized (or something in between)? Here are three approaches to figuring out their probable adult weight, ranked by accuracy.

Knowing how big your puppy will get can help you make important decisions.

Which type of food to feed (and how much), what size of dog crate to buy, whether to rent an apartment or put a down payment on that house with the big yard… we’re talking major stuff.

But without a crystal ball, predicting a dog’s adult size can be tough. After all, it’s influenced by a myriad of factors, including:

  • Breed. Perhaps unsurprisingly, breeds are responsible for the greatest variance in adult height and weight among dogs. There’s a reason you don’t see 50 lb. Chihuahuas or teacup Mastiffs—breeders must meet certain standards for their litters to be considered purebred.
  • Neuter/spay status. According to studies, neutering or spaying before about nine months appears to slightly increase a dog’s adult size, whereas neutering after such time slightly decreases it. This likely has to do with the hormonal response to the procedure.
  • Sex. Across breeds, adult male dogs tend to be a little larger than their female counterparts.

Despite the many variables, it is possible to figure out (approximately) how big your dog will get. Here are three approaches to try, ordered by least accurate to most.

Small dog lying on top of a big dog
Dogs grow at different rates based on their breeds. So, it’s helpful to know your pup’s ancestry.

Low accuracy: Calculate adult weight using a formula.

You may have already tried one of the many dog size prediction calculators online. At their core, these tools rely on generic formulas that take into account your pup’s current weight and age (and, in some cases, breed).

For example, here’s a formula that Wisdom Panel™ veterinarians recommend: Multiply your pup’s weight at four months by two to get an estimate of their adult weight. So, if your dog weighs 15 lb. at four months, their adult weight may be around 30 lb. (give or take a few pounds).

Seems a little too easy, right? The catch is that different breeds grow at different rates. Toy dog breeds, for example, often reach their adult size by as early as eight months, whereas giant breeds may not stop growing until up to two years. So, figuring adult size with a formula or calculator is far from perfect.

Puppy touching noses with parent dog
Knowing your dog’s ideal adult weight can help you plan for their nutrition and exercise needs.

Medium accuracy: Consider breed averages and parentage.

Know your dog’s breed(s)? One relatively reliable way to predict their adult size is to reference breed averages. We recommend checking the Wisdom Panel™ breed library—where you’ll find typical height and weight ranges for hundreds of dog breeds.

The sizes of your pup’s parents may also provide a good idea of what you can expect. But if you adopted a mystery mix from the shelter, you likely don’t know much about their parentage or breeds. In such a case, you’re better off trying a different approach.

Pro tip: Don’t be misled by visual characteristics. You might have heard that the size of a puppy’s paws indicates how big they’ll get. But some dogs just have large (or small) feet relative to their body size.

Example of Wisdom Panel™ ideal adult weight range predictions
Ideal weight range predictions are among the many benefits Wisdom Panel™ dog DNA tests offer.

High accuracy: Predict size potential based on DNA.

Even among purebred dogs, variances in size may exist. Why? Some breeders prefer slightly smaller or larger dogs than show standards dictate. And many environmental factors—including nutrition and illness—can impact adult height and weight potential.

Ultimately, the best solution is to look for genetic clues about how big your one-of-a-kind dog will get. Wisdom Panel™ DNA tests offer ideal adult weight range predictions based on multiple genetic markers related to size—as well as your dog’s breed mix—resulting in a far more precise prediction of your pup’s mature size. (You also get to see their breed mix down to 1%, screen for health risks, and much more.)

Ready to know how big your puppy will get?

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