What age do puppies stop growing?

When a new puppy arrives, one of the first questions most dog lovers ask is “How big will they get, and when will they stop growing?” That timing matters more than vanity: it guides what size bed you buy, which toys are safe, when to limit high-impact play, and even when to schedule certain surgeries or targeted training milestones. Understanding growth windows helps set realistic expectations and protect joints, behavior, and long-term health.

How knowing when puppies finish growing helps you plan care and training

Choosing the right toys, bedding, and crate sizes depends on a good estimate of adult size; a crate that’s too small can stress a growing spine, while oversized toys can be a choking hazard for small breeds. Vaccinations and routine vet checks follow a schedule that dovetails with rapid developmental stages—missing those windows can leave a pup vulnerable. Training and socialization are also age-dependent: social risk periods and fear imprinting may be easier to manage when you know how quickly your pup is changing physically and emotionally. Finally, owners who expect an adult temperament or energy level before their dog has finished maturing often misread normal adolescent behavior for permanent traits.

Age-by-size snapshot: when small, medium and large breeds typically stop growing

• Small breeds (toy and small companions): roughly 9–12 months for most growth to slow, though some filling out may continue a few months after that.
• Medium breeds (retrievers, spaniels): roughly 12–15 months before most linear growth is complete.
• Large breeds (Labradors, German Shepherds): roughly 12–18 months; many keep adding height through 15–18 months.
• Giant breeds (Great Danes, Mastiffs): roughly 18–24+ months. Weight and muscle mass may continue changing after the bones have mostly stopped lengthening; skeletal maturity and full adult body weight can be separate timelines.

What’s happening inside: bones, hormones and growth plates explained

Bones lengthen at specialized regions called epiphyseal or growth plates. These are softer, cartilage-rich zones near the ends of long bones that add new cells and push the bone longer as the puppy grows. When the growth plates “close” they ossify and the bone no longer lengthens; that closure happens at different times depending on the bone and the breed.

Growth is coordinated by a hormonal interplay. The growth hormone/IGF-1 axis (growth hormone released by the pituitary stimulating insulin-like growth factor 1 from the liver and tissues) is a major driver of rate and pattern, and nutrition modifies how strongly that system can work. Sex hormones—estrogens and androgens—rise with puberty and are major signals that accelerate growth plate closure, which is why the timing of puberty influences final height.

Genetics sets the basic plan. Breed-specific genes determine how fast growth runs early on and when the system should wind down. Some breeds are ‘programmed’ to grow quickly and finish early; others have a prolonged juvenile phase. I typically see the fastest, most obvious growth in the first three to four months, with rates slowing but continuing to add significant height and weight for many months after.

Key factors that speed up or slow a puppy’s growth — genetics, diet and health issues

Breed size and family genetics are the largest determinants—siblings and parents are often good predictors of a puppy’s adult frame. Nutrition plays a large supporting role: poor nutrition can stunt growth while excess calories, especially in large and giant breeds, may cause unnaturally rapid weight gain that stresses immature joints. Protein quality and calorie balance matter more than single ‘fad’ ingredients.

The timing of spay/neuter can influence how hormones affect growth plates. Early removal of sex hormones may delay growth plate closure, potentially allowing longer bone growth but also possibly increasing risk for some joint problems in certain breeds. This is an area of active study and recommendations can vary depending on breed, size, and health risks.

Health problems—congenital endocrine disorders, chronic illness, or orthopedic conditions—can slow or distort growth. Activity level and exercise type also shape musculoskeletal development: repetitive high-impact jumping or heavy loading before the skeleton stabilizes may increase risk of injury.

Warning signs to watch for: delayed growth, limping, swollen joints and appetite changes

Watch your puppy’s growth curve. A consistent failure to gain weight, or a plateau well below the expected trajectory for the breed, is a reason to seek veterinary evaluation. Conversely, very rapid, disproportionate weight gain—especially if a puppy looks top-heavy or has awkward gaits—can suggest nutritional imbalance or an underlying endocrine problem.

Persistent limping, reluctance to put weight on a limb, or asymmetric limb length or swelling near an elbow or knee should prompt an exam and possibly X-rays; these signs may point to growth plate injury, infection, or joint disease. Systemic signs such as ongoing lethargy, poor appetite, recurrent vomiting or diarrhea, or delayed developmental milestones are also reasons for early veterinary attention.

Practical owner checklist: feeding, vet checks and exercise guidelines for growing pups

1. Start a simple growth chart: weigh your puppy weekly for the first six months, then every two to four weeks until maturity. Measure body length and height at the shoulder monthly for longer-monitoring breeds. Record and bring this to the vet—trends are more informative than single numbers.
2. Feed according to age and breed-size guidelines. Use a commercial diet formulated for puppies, and follow feeding recommendations for your dog’s expected adult size unless your vet suggests adjustments. Avoid abrupt diet changes and extra table scraps that add empty calories.
3. Schedule routine wellness exams and discuss X-rays if growth feels abnormal. Radiographs can show growth plate status and reveal conditions like panosteitis or retained cartilage fragments that may explain limping or discomfort.
4. Talk with your veterinarian about timing of spay/neuter for your breed. For some large and giant breeds, delaying neuter until skeletal maturity may be recommended; in other cases, early neuter may be appropriate for behavioral or population-control reasons.
5. Adopt joint-protection strategies early: control body condition, avoid overfeeding, and moderate high-impact exercise. If there’s breed risk for joint disease, discuss evidence-based supplements or medical strategies with your vet before starting them.

Shaping behavior and protecting developing bodies — training and home-setup tips

While puppies are still growing, limit high-impact tasks like repeated jumping on and off furniture, frequent stair-climbing for very young large-breed puppies, or rough sled-type pulling. Use ramps and pet steps to reduce strain on hips and shoulders. Non-slip surfaces help prevent awkward slips that can stress immature joints.

Behaviorally, continue age-appropriate socialization but avoid forcing long, tiring sessions. Short, frequent training sessions that reward calm behavior fit the changing attention span of a growing dog. Adolescence may bring testing and increased reactivity; remembering the puppy is still maturing physically can help you choose training that reduces anxiety and prevents injury from overexuberant play.

Rotate toys to reduce repetitive stress on the same areas—for example, heavy chew sessions on hard toys can wear teeth and transmit force to jaws and neck. Use front-clip harnesses for puppies that pull on leash to avoid pressure on the trachea and neck, especially while the skeleton is still maturing.

Picking safe gear as they grow: collars, harnesses, beds and toys that adapt

Practical tools make monitoring and protection straightforward: a digital scale at home helps you track weight consistently; a soft measuring tape lets you record height and length. Front-clip harnesses are often safer than neck collars for pullers. Ramps, pet steps, and non-slip mats reduce forced jumping and slipping in the home. If you’re considering joint supplements, ask your veterinarian—some products are appropriate for risk reduction, but timing and formulation matter and are best guided by a professional.

For breeds at higher risk of orthopedic disease, consider periodic orthopedic evaluations or radiographic screening at key developmental stages. In my experience, owners who pair careful monitoring with gentle environmental modifications almost always avoid preventable injuries and have an easier time through adolescence.

Vet-reviewed sources and further reading

• Merck Veterinary Manual: “Growth and Development of the Dog” — Merck & Co., Inc.; provides clinical details on growth plate closure and developmental milestones.
• American Veterinary Medical Association (AVMA): “Pediatric Spay/Neuter” guidance and policy statements on timing and considerations for small animal sterilization.
• World Small Animal Veterinary Association (WSAVA) Global Nutrition Toolkit: “Growth and Weaning” — practical guidance on puppy nutrition and feeding for different breed sizes.
• Nelson, R. W., and Couto, C. G., Veterinary Internal Medicine: “Growth Disorders and Endocrine Influences” — chapter overview on hormonal control and pathologic causes of abnormal growth.
• Piermattei, D. L., Flo, G. L., and DeCamp, C.: Handbook of Small Animal Orthopedics and Fracture Repair — reference for growth plate injuries and orthopedic management in growing dogs.