Watching your puppy grow up is one of the best parts of being a pet parent. From tiny paws and clumsy zoomies to full-grown confidence and personality, the journey is filled with big changes. But many dog owners find themselves wondering: when do dogs stop growing? The answer depends on several factors—size, genetics and even whether your dog is a mixed breed. In this guide, we’ll walk through what growth looks like at every stage, what to expect for different breeds, and how your dog’s growth compares to human development.
When Do Puppies Stop Growing?
Puppies grow fast—especially in the beginning. You will likely see rapid changes in the early stages that slow over time.
0–6 Months
During the first few weeks, puppies double and triple in size. Growth occurs in spurts, especially during the first 6 months, when puppies go through rapid changes in height, weight, muscle tone and coordination.
6–9 Months
Most puppies experience their final noticeable growth phase around 6 to 9 months old. During this time, growth plates in the bones are gradually closing, signaling the end of physical development. Still, some changes, like filling out or muscle definition, may continue for several more months.
12–24 Months
Most dogs are considered adults between 12 and 18 months old, but this can stretch to 24 months for large and giant breeds. Once the growth plates are fully closed, a dog is considered physically mature. Emotional and behavioral maturity might take a little longer. Even after your dog is fully grown physically, you may still see puppy-like energy, excitement and curiosity. Their personalities and behaviors will continue to evolve as they mature emotionally.
These are general guidelines, but every dog is different. Your veterinarian can help determine when your puppy has officially entered adulthood based on a physical exam.
How Does a Dog’s Size Affect Their Growth?
A dog’s breed and size can help determine when they will be fully grown. Large and extra-large dogs tend to take longer to reach physical maturity.
In general:
- Small dogs: Fully grown by 8–12 months
- Medium dogs: Fully grown by 12–15 months
- Large dogs: Fully grown by 18–24 months
Small Dogs
Small dog breeds like Dachshunds, Pomeranians and French Bulldogs typically grow up fast, reaching full size by 12 months of age. Their compact bodies and fast metabolisms allow them to complete physical development sooner than their larger canine counterparts.
If you have a small breed dog, you may notice them slowing down in height and weight gain as early as six months old. However, they may continue to fill out in the chest and build muscle tone into their second year.
Medium Dogs
Mid-sized dogs such as Beagles, Cocker Spaniels and Border Collies fall somewhere in the middle, usually finishing growth by 15 months. These dogs have a slightly longer growth period than smaller breeds but won’t take as long as large or giant dogs.
During this stage, you’ll notice steady but not dramatic changes. It’s important to continue feeding a puppy-appropriate diet until your veterinarian recommends transitioning to adult food.
Large Dogs
Large and giant breeds, such as Labrador Retrievers, Rottweilers and Great Danes, can continue growing until 24 months of age. Their long bones need more time to fully develop, and their joints are more susceptible to stress during growth.
It’s especially important not to over-exercise large breed puppies or feed them diets too high in calcium or calories, as this can lead to joint problems later in life. Regular check-ins with your vet will help make sure your big pup is growing at a healthy pace.
When Do Mixed Breed Dogs Stop Growing?
Mixed breed dogs are a bit more unpredictable when it comes to growth. Their final size depends on the genetic mix passed down from their parents. If your mixed-breed pup has two small-breed parents, it’s likely they’ll mature around 8–12 months. But if they have a large-breed parent in the mix, they may continue growing into their second year.
Some clues can help estimate how big your mixed-breed puppy will get:
- Paw size: Big paws often mean a bigger adult dog
- Growth trends: Consistent weight and height increases give you a sense of their trajectory
- DNA tests: These can provide insight into breed makeup and adult size predictions
Dogs’ Growth Rate Compared to Humans
Dogs grow much faster than humans. In fact, during their first year of life, a dog can mature at the equivalent of 15 human years. But that pace slows down after the first year. While the “1 dog year = 7 human years” rule is a rough estimate, it’s not entirely accurate—especially during puppyhood.
Here’s a general idea:
- First year: Dogs reach adolescence and sexual maturity—equivalent to a teenager or young adult human
- Second year: Most dogs are considered full adults
- After that: Each year roughly equals 4–5 human years, depending on breed size
Understanding this difference helps explain why dogs grow so quickly—and why proper nutrition and care in the early months is so crucial.
