Most dogs reach their full height between 6 and 18 months of age, but they continue filling out with muscle and body mass for several months after that. The exact timeline depends almost entirely on your dog’s expected adult size. A five-pound Chihuahua finishes growing in a fraction of the time it takes a 150-pound Great Dane.
Growth Timelines by Breed Size
Smaller dogs mature faster. Toy and small breeds (under about 20 pounds) typically reach their full adult size by 10 to 12 months. Medium breeds (20 to 50 pounds) generally finish growing around 12 to 15 months. Large breeds (50 to 80 pounds) need 12 to 18 months. Giant breeds like Mastiffs, Great Danes, and Saint Bernards can keep growing until they’re 18 to 24 months old.
These ranges apply to overall physical size, meaning both height and weight. But height and weight don’t finish on the same schedule, which is where things get a little more nuanced.
Height Finishes Before Weight
Dogs reach their full standing height before they reach their full body weight. Most puppies are close to their adult height by 6 to 12 months, but they spend another 6 to 18 months after that filling out their frame. During this later phase, your dog is building muscle, broadening through the chest, and developing the denser body composition of an adult. Bones and joints reach their final size around the one-year mark for small and medium breeds, and closer to two years for large and giant breeds. Muscles, internal organs, and the immune system continue maturing on a similar timeline.
This is why a one-year-old Labrador can look tall but lanky. The skeleton is nearly done, but the body hasn’t caught up yet. That “gangly teenager” phase is completely normal, and it resolves on its own as the dog finishes filling out.
Growth Plates and Why They Matter
A puppy’s long bones (legs, spine) grow from soft areas of cartilage near the ends of each bone, called growth plates. As the dog matures, these plates gradually harden into solid bone, and once they close, the bone stops lengthening. Growth plate closure is what determines when your dog has truly finished getting taller.
In small breeds, the plates close earlier, often by 6 to 9 months. In large and giant breeds, they stay open longer, sometimes past 12 to 15 months. This has real practical consequences. While growth plates are still open, they’re softer than the surrounding bone and more vulnerable to injury. High-impact exercise, repetitive jumping, and intense training on hard surfaces carry more risk for a puppy whose plates haven’t closed yet. This is especially relevant for large and giant breed puppies, whose plates remain open well into their second year.
How Spaying and Neutering Affects Growth
The timing of spaying or neutering can influence how your dog’s bones develop. Sex hormones play a role in signaling growth plates to close. When those hormones are removed early through sterilization, the plates may stay open slightly longer, allowing the bones to grow a bit more than they otherwise would. This can result in a subtly taller, leggier build, and some research links it to a higher risk of orthopedic problems in large breeds.
The American Animal Hospital Association recommends sterilizing small breeds around 5 to 6 months of age, but waiting until growth stops for large breeds, roughly 9 to 15 months depending on the individual dog. For female large-breed dogs, the decision involves balancing orthopedic risk against the benefits of reducing mammary tumors and preventing unwanted litters. Your vet can help you weigh these tradeoffs based on your dog’s specific breed and circumstances.
Signs Your Dog Is Still Growing
Paw size is the classic clue. Puppies with oversized paws relative to their legs and body almost certainly have more growing to do. You can also look at the overall proportions: a dog that appears long-legged and narrow through the chest is likely still filling out, even if it seems to have reached its adult height.
Loose skin is another indicator. Puppies often have skin that seems a size too big, particularly around the neck and shoulders. As they build muscle mass and broaden, the skin fits more snugly. If your dog still has that slightly baggy look, it’s probably not done yet.
For a more precise estimate, breed-specific growth charts from veterinary sources like the WALTHAM Petcare Science Institute plot expected weight against age for different size categories. If you know your dog’s breed or expected adult weight, these charts can help you see roughly where your puppy falls on the curve and how much growing is left.
Nutrition During the Growth Period
What you feed a growing puppy directly affects how its skeleton develops. Puppy food is formulated with higher levels of calories, protein, calcium, and phosphorus to support rapid bone and muscle growth. Most dogs should stay on puppy food until they’ve reached their full adult size, which means small breeds can switch to adult food around 12 months, while large and giant breeds benefit from staying on a large-breed puppy formula for 12 to 24 months.
Overfeeding a large-breed puppy is a common and underappreciated mistake. Excess calories don’t make bones stronger; they make the puppy grow too fast, which puts stress on developing joints and increases the risk of conditions like hip dysplasia. Large-breed puppy foods are specifically designed to support steady, controlled growth rather than maximum growth speed. The goal is for your dog to reach its genetically determined adult size on a healthy timeline, not to get there as fast as possible.