How to Predict a Puppy’s Size

There’s no foolproof way to predict a puppy’s size. However, one may consider a dog’s weight, litter size, and other related factors to make an educated guess.

Apr 13, 2023By Colt Dodd
how to predict puppy size

A potential pet parent’s visiting the Humane Society, and it’s puppy love at first sight. Yet, while holding a squirming, eight-week-old pup, there’s just one last thing to clear up: “How big is this guy supposed to get, anyway?”

Knowing a puppy’s adult size is important when adding a furry friend to the household. After all, there’s a big difference between caring for a 100-pound Great Dane and a 10-pound Maltese. Here, one can learn how to predict a puppy’s size. Some suggestions include testing the dog’s breed and meeting its older siblings.

Suggestions for Predicting a Puppy’s Size

nine dog breeds in a collage

There’s no foolproof way to predict a puppy’s size. However, not everyone has the luxury of the “wait-and-see” approach. Some suggestions when assessing a puppy’s potential size include:

Weighing the Puppy

There are formulas for predicting a puppy’s size based on its weight once it reaches a certain age. Take a Yorkshire terrier, for instance. An owner can weigh the puppy at six weeks, then times that weight by four. So, if a Yorkie weighs one pound at six weeks, chances are, they’ll weigh four pounds when fully grown.

This formula varies depending on the dog’s breed. In another example, consider an English Mastiff. Here, an owner would use a different formula. They would multiply the dog’s weight at six months by two.

dog visiting the vet doctor

At six months, these giant puppies can weigh anywhere from 60 to 80 pounds! This means, using the formula outlined above, the dog will likely weigh more than 120 pounds when fully grown.

Consider this table to understand more:

Size TypeBreed ExamplesFormula
Toy BreedChihuahuas, Yorkshire Terriers, & Italian Greyhounds(Weight at six weeks) x 4
Small Breeds Jack Russells and Shiba Inus (Weight at six weeks) x 4
Medium Breeds Australian Shepherds and Border Collies (Weight at 14 weeks) x 2 + (1/2 weight at 14 weeks)
Large Breeds i.e., German Shepherds(Weight at six months) x 2
XL Breeds Great Danes and Irish Wolfhounds (Weight at six months) x 2

Getting a Dog DNA Test

Make no mistake: most dog DNA tests aren’t about learning a puppy’s paternity. Instead, these tests determine a dog’s breed (or breeds, in some cases). Some tests, like Wisdom Panel, claim to measure a dog’s breed with 98 percent accuracy. These tests generally cost around $80.

dog DNA test science chemistry

Here’s what to know about these tests:

  • Pet owners don’t have to schedule a vet visit to determine their dog’s breed. One can perform a dog DNA test at home. Most tests require the pet parent to swab the inside of the dog’s mouth with a Q-tip. Then, they send the test away and wait for the results.
  • These tests measure dog breeds––not size. Even in a single dog breed, canines can vary in size. For instance, imagine a dog DNA test classifies a puppy as a poodle. However, there are different poodles—standard poodles, French poodles, miniature poodle. While this can offer a ballpark estimate of a dog’s size, it’s not the answer many may search for.
  • Dog DNA tests don’t just test breeds. They can also predict the health problems a puppy may experience throughout its lifetime. Some even offer specific caretaking instructions based on a dog’s genetic predisposition.

Learning the Litter’s Size

The American Kennel Club (AKC) reports that the larger a dog, the larger its litter. Take Cane Corsos, for instance. Also known as Italian mastiffs, these 110-pound giants routinely have sizeable litters. The same can’t be said for French Bulldogs, which seldom have litters exceeding four puppies.

three puppies drinking mother_s milk

If they have the opportunity, a pet parent should ask how big the puppy’s litter is. This could add yet another clue when determining the dog’s grown-up size.

Meeting the Puppy’s Older Siblings

When someone adopts a puppy from a rescue, chances are, they won’t meet the dog’s older siblings. However, people who buy their dogs from responsible breeders might have this opportunity.

Meeting a puppy’s older sibling offers a solid indicator of how big it’ll be. Keep in mind that puppies’ sizes can range from litter to litter. It’s not uncommon for a dog mama to have eight small puppies in one litter, then have a single, monster-sized puppy the next.

Taking the Dog to the Vet

Unless a dog’s greying around the muzzle, it’s hard to tell its exact age. However, a veterinarian can determine a dog’s age (and, by extension, its possible weight) by examining its teeth. Worn-down, missing teeth point to an older dog. Yet, unerupted adult teeth could point to a dog that hasn’t reached the six-month mark.

Only Time Will Reveal a Puppy’s Full-Grown Size

newborn puppies in a basket

Learning a puppy’s adult weight is just one of many things parents should consider when adopting a new forever friend. That’s because weight isn’t necessarily an indicator of a dog’s temperament.

For instance, many people shy away from adopting greyhounds because they can be 80 pounds when fully grown. Yet, these gentle giants are notorious couch potatoes, needing very little exercise. The same can’t be said for the smaller Jack Russell, which requires constant stimulation despite its tiny stature. Bottom line: dogs need attention, both big and small, young, and old. For more information on caring for a new puppy, check out this article from the Humane Society of the United States.

Colt Dodd
By Colt Dodd

Colt Dodd is a sighthound enthusiast with three years of freelance writing experience. He has an Italian greyhound/Shetland sheepdog mix named Homer. In his spare time, he enjoys going to dog parks and writing fiction.