When do dogs stop growing?

Although predicting your puppy’s size isn’t an exact science, a puppy-weight calculator could help guess your purebred or mixed breed’s adult weight.


Most dogs stop growing between the ages of six and 18 months. Dog owners can use a puppy-weight calculator to predict a dog’s adult weight based on size and breed.

Two common concerns among new dog owners are how long puppies spend growing and how big they’ll end up. The simple answer is that puppy growth rate depends on dog breed and size. In general, most dogs stop growing between the ages of six and 18 months. Some extra large breeds, though, can continue to grow up to 24 months. Small dogs finish their growth periods earlier than larger dogs, though this largely depends on the breed. Gender matters, too, as male dogs usually outweigh females across all breeds.

Purebred dog breed owners can use a puppy-weight calculator based on breed standards to help predict progress. And nowadays, you can even find a mixed breed puppy weight calculator to provide the best guess based on your pet’s breed mixes, age, and current weight.

How big will my puppy get?

Dog breed standards help tell us how big purebred puppies will get. Sizes of dogs range widely from tiny Chihuahuas, averaging around 4 pounds, to 200-plus-pound Mastiffs. Naturally, pedigree plays a role as well, as many lines and litters of dogs are bred with size in mind. However, purebred dogs should still have a reasonable expectation to wind up within a certain weight window by adulthood.

When it comes to mixed breeds, things get more complicated. It helps to know the dog breeds and sizes of the dog’s parents, but this isn’t always possible. In these cases, best guesses are made based on calculations like size and suspected dog breed.

Are puppy weight calculators accurate?

There are several puppy weight calculators available online, but their accuracy is a subject of debate. Simply put, these tools, especially mixed breed puppy-weight calculators, use formulas based on inexact science. For instance, one formula recommends multiplying a puppy’s weight at 4 months old by two to estimate the predicted adult weight. The idea here is that dogs stop growing at an average of 8 months old. However, other factors also come into play, including gender and whether or not your dog has been spayed or neutered.

Most puppy-weight calculators are based on established studies and dog breed standards, so you can expect some measure of accuracy. However, don’t fret if the estimates end up off by a bit. Your pup may wind up larger than you’d planned, but if you’ve prepared properly, size shouldn’t matter all that much. What truly matters is providing your growing puppy with the best possible life so they’ll grow into a happy and healthy adult dog.

The following puppy growth chart is from the American Kennel Club and is an approximation. There’s no guarantee of how quickly (or slowly) your dog will grow.

Puppy Growth Chart For Predicting Dog Size
Small (0-20 lbs)Medium (21-50 lbs)Large (51-100 lbs)X-Large (100+ lbs)
6 months75% fully grown66%60%50%
9 months90%85%75%65%
12 months100%95%85%80%
15 months100%100%95%90%
18 months100%100%100%100%