All puppies are considered adult dogs when they are one year old. However, puppies will also continue to grow in both size and height as long as their bones are developing. This can take 6-24 months depending on the dog.
A puppy’s skeletal growth will determine how tall they will become as an adult dog. But, muscles and fat can still fill in once their bones are done developing, which can also affect their overall size even if it doesn’t necessarily affect their height.
Smaller Dog Breeds Tend to Finish Growing Faster Than Large Breeds
Small dog breeds, and even medium-sized dog breeds, tend to finish developing more quickly than larger breeds. Because they tend to stay small, they don’t typically require as much time to develop.
Many small dog breeds tend to stop growing when they are 6-8 months old. Medium dog breeds tend to take a bit longer and, on average, reach their adult size when they are around one year old.
Larger Dog Breeds Tend to Need More Time to Finish Growing
It takes time to grow into those longer and bigger bones! Larger dog breeds tend to continue to grow until they are 12-18 months of age. However, this depends completely on the size of your dog. If your dog breed is a giant breed that tends to weigh more than 70 pounds as an adult, they may continue growing until they are 2 years old.
Purebred Dogs are Easier to Predict Than Mixed Breeds
Purebred dogs are more predictable when it comes to their traits and characteristics while mixed-breed dogs are more variable and unpredictable. Because we have a better idea of what to expect in the overall size, temperament, etc. in a purebred dog, it’s easier to estimate a range of when they will finish growing as puppies.
The final size and development timeline are more difficult to predict in a mixed-breed dog. You can work with your vet to determine when your mixed-breed puppy is done growing. If you can still feel the “knobs” of the ribs when you run your hands down a puppy’s rib case, you are feeling the growth plates of the ribs. This means your puppy is still growing and their bones are still developing. Your vet will know what these feel like and can help you determine whether your puppy’s bones are still developing during their puppy checkups.