At What Age Do Dogs Stop Growing? The Science of Canine Development
At what age do dogs stop growing? Learn the science behind canine growth timelines by breed size, growth plate closure, and what it means for your dog's health.
The Quick Answer: When Do Dogs Stop Growing?
Most dogs reach their full adult size between 6 and 24 months of age, depending on breed size. Small breeds (under 20 lb / 9 kg) typically stop growing by 8–12 months. Medium breeds (20–50 lb / 9–23 kg) finish growing around 12–15 months. Large breeds (50–100 lb / 23–45 kg) continue growing until 15–18 months, while giant breeds (over 100 lb / 45 kg) may not reach full skeletal maturity until 18–24 months. However, dogs often continue filling out with muscle and fat for several months after their bones stop lengthening.
The Science Behind Canine Growth: How Bones Get Longer
Dogs grow taller because of specialized cartilage regions called growth plates (technically known as epiphyseal plates) located near the ends of their long bones — the femur, tibia, humerus, and radius. These plates contain rapidly dividing chondrocytes (cartilage cells) that produce new tissue, which gradually calcifies into bone through a process called endochondral ossification.
As a dog approaches skeletal maturity, rising levels of sex hormones — primarily estrogen in both males and females — signal the growth plates to slow their cell division and eventually close completely. Once a growth plate has fused (ossified), that bone can no longer increase in length. This is the biological mechanism that determines when a dog stops growing taller.
Research published in the Journal of Veterinary Internal Medicine has documented that growth plate closure timing correlates strongly with predicted adult body mass. A study by Salt et al. (2020) analyzed over 50,000 dogs across 48 breeds and confirmed that larger breeds maintain open growth plates significantly longer than smaller breeds — sometimes by as much as 12–14 months of additional growth time.
This has a direct clinical implication: spaying or neutering before growth plates close can delay that closure (since sex hormones drive the process), potentially resulting in slightly longer limbs and altered joint angles. A 2020 study in Frontiers in Veterinary Science found that early-neutered Golden Retrievers had a statistically higher incidence of hip dysplasia and cranial cruciate ligament tears compared to dogs neutered after 12 months. Always consult your veterinarian about the optimal timing for your individual dog.
Growth Timelines by Breed Size: What the Data Shows
| Size Category | Adult Weight | Growth Plates Close | Full Height Reached | Full Weight/Muscle Mass | Example Breeds |
|---|---|---|---|---|---|
| Toy/Small | Under 20 lb (9 kg) | 6–8 months | 8–10 months | 10–12 months | Chihuahua, Pomeranian, Yorkshire Terrier |
| Medium | 20–50 lb (9–23 kg) | 10–12 months | 12–14 months | 15–18 months | |
| Beagle, Border Collie, Australian Shepherd | |||||
| Large | 50–100 lb (23–45 kg) | 14–16 months | 15–18 months | 18–24 months | |
| Labrador Retriever, German Shepherd, Rottweiler | |||||
| Giant | Over 100 lb (45 kg) | 18–20 months | 18–24 months | 24–36 months | |
| Great Dane, Saint Bernard, Mastiff, Irish Wolfhound |
The numbers above represent population-level data from the AKC and veterinary growth-curve research. Individual dogs may vary by several weeks in either direction. Genetics, nutrition, and health status all influence growth rate.
Why Larger Dogs Grow Slower: The Evolutionary and Physiological Context
From Wolves to Chihuahuas: An Evolutionary Puzzle
All domestic dogs (Canis lupus familiaris) share a common ancestor with gray wolves, which typically reach full skeletal maturity around 12–14 months. Through thousands of years of selective breeding, humans created an extraordinary range of body sizes — from the 4 lb (1.8 kg) Chihuahua to the 200 lb (90 kg) English Mastiff. This represents a roughly 50-fold difference in body mass within a single species, unmatched in the mammalian world.
The reason giant breeds take longer to grow is rooted in simple physics and biology: building a larger skeletal frame requires more time for cartilage proliferation, mineral deposition, and structural remodeling. A Great Dane puppy must generate roughly 100 times more bone tissue than a Chihuahua puppy to reach adult size, yet both start from similarly sized embryos. The growth plates in giant breeds remain active longer to accommodate this demand.
Interestingly, the IGF-1 gene (insulin-like growth factor 1) has been identified as a primary regulator of body size in dogs. A landmark 2007 study in Science found that a single variant of this gene accounts for much of the size difference between small and large breeds. Small breeds carry a variant that limits IGF-1 production, effectively capping growth earlier — a trait that likely originated in Middle Eastern wolf populations over 12,000 years ago.
How Is Dog Growth Different From Human Growth?
Humans typically grow for 16–20 years, with growth plates closing during late adolescence. Dogs compress this entire process into 6–24 months — meaning a dog's growth rate, especially in the first six months, is dramatically faster than a human child's.
A Labrador puppy may gain 2 lb (0.9 kg) per week during peak growth (months 2–4), while a human infant gains roughly 1–2 lb (0.5–0.9 kg) per month. This rapid skeletal development is why proper nutrition during puppyhood is critical — both underfeeding and overfeeding can cause lasting structural problems.
One key difference: human long bones grow primarily at two growth plates per bone (one at each end), while the timing of closure is more sequential and predictable. In dogs, different bones and even different ends of the same bone may close at slightly different times, which is why some puppies appear "leggy" or disproportionate during certain growth phases.
What Growth Means for Daily Life: Practical Implications for Owners
Nutrition During Growth
- Small/medium breeds: Feed a diet labeled "complete and balanced for growth" (AAFCO statement) until approximately 10–12 months, then transition to adult maintenance food.
- Large/giant breeds: Use a large-breed puppy formula specifically designed with controlled calcium (1.0–1.6% on a dry matter basis) and moderate caloric density. These formulas slow growth rate to reduce orthopedic disease risk. Continue until 12–18 months depending on breed size.
- Avoid overfeeding: Excess calories accelerate growth rate and increase mechanical stress on developing joints. According to the Merck Veterinary Manual, large-breed puppies fed free-choice have higher rates of hip dysplasia and osteochondrosis compared to those on portion-controlled feeding.
Exercise During Growth
- Rule of thumb: Structured exercise (walks, hikes) should be limited to roughly 5 minutes per month of age, twice daily until growth plates close. A 4-month-old puppy gets about 20-minute walks; an 8-month-old gets about 40 minutes.
- Avoid high-impact activity (agility jumps, long-distance running on hard surfaces, repetitive stair climbing) until your vet confirms growth plate closure via X-ray — typically around 12–18 months for large breeds.
- Free play is generally fine: Dogs self-regulate during unstructured play. The concern is forced, repetitive exercise that a dog cannot opt out of.
Spay/Neuter Timing
- Current veterinary consensus (per the AVMA and multiple breed-specific studies) suggests that for large and giant breeds, delaying spay/neuter until after growth plates close (12–18 months for males, after first heat cycle for females) may reduce the risk of certain orthopedic conditions and some cancers.
- For small breeds, early spay/neuter (around 6 months) carries fewer orthopedic risks since growth plates close earlier.
- Always discuss timing with your veterinarian based on your dog's breed, sex, and individual health profile.
Common Misconceptions About Dog Growth
| Myth | Fact |
|---|---|
| "A dog's paws tell you how big they'll get." | Paw size is a rough indicator at best. Some puppies have disproportionately large paws during growth spurts that don't correlate with final adult size. Genetics and breed standards are far more reliable predictors. |
| "All dogs stop growing at 1 year old." | This is true only for small to medium breeds. Large and giant breeds continue skeletal growth well past 12 months, and may not reach full muscle mass until 2–3 years. |
| "Feeding more makes a puppy grow bigger." | Overfeeding makes a puppy grow faster and gain excess fat, but it doesn't increase genetically predetermined adult size. Rapid growth actually increases the risk of developmental orthopedic diseases like hip dysplasia, osteochondrosis dissecans (OCD), and hypertrophic osteodystrophy (HOD). |
| "Mixed-breed dogs always grow faster than purebreds." | Growth rate depends on the size category of the dog, not whether it's purebred or mixed. A mixed-breed dog with Great Dane ancestry will still take 18–24 months to mature. |
| "Once a dog is neutered, they stop growing." | Neutering actually delays growth plate closure by removing sex hormones. Early-neutered dogs may grow slightly taller than intact counterparts, though the clinical significance varies. |
| "A dog that's still growing can't be trained." | Training and growth are independent processes. Positive reinforcement training can begin as early as 8 weeks. Just avoid physically demanding exercises until skeletal maturity. |
When Growth Patterns Signal a Problem
Most growth variations fall within normal ranges, but certain signs warrant a veterinary evaluation:
- Limping or shifting leg lameness in a growing puppy — could indicate panosteitis ("growing pains"), hypertrophic osteodystrophy, or osteochondrosis. These conditions are most common in large breeds between 3 and 12 months.
- Stunted growth or failure to gain weight — may signal parasitism, portosystemic shunt (a liver vascular anomaly common in small breeds), growth hormone deficiency, or severe malnutrition. A puppy that consistently falls below the 10th percentile for breed weight curves should be evaluated.
- Asymmetric growth — if one limb appears shorter or more angular than its counterpart, this may indicate premature growth plate closure (often caused by trauma) leading to angular limb deformity. This is most commonly seen in the radius/ulna of chondrodystrophic breeds like Dachshunds and Basset Hounds.
- Delayed growth plate closure — sometimes detected on X-ray, this can be associated with hypothyroidism, retained juvenile reproductive hormones, or certain nutritional deficiencies.
- Visible pain during exercise or reluctance to move — growing puppies should be energetic and willing to play. Persistent stiffness, bunny-hopping gait, or reluctance to jump could indicate early hip or elbow dysplasia.
If you notice any of these signs, consult your veterinarian promptly. Early intervention — whether through dietary adjustment, activity modification, or surgical correction — often produces better long-term outcomes.
Related Developmental Milestones
Understanding when dogs stop growing is just one piece of the developmental picture. Here's how other milestones align with the growth timeline:
- Dental maturity: All 42 adult teeth typically erupt by 6–7 months, well before skeletal growth is complete.
- Sexual maturity: First estrus (heat cycle) in females occurs between 6–12 months for small breeds and 12–24 months for giant breeds. Males may show reproductive behavior as early as 5–6 months.
- Emotional/behavioral maturity: Most dogs reach full behavioral maturity between 18–36 months. Giant breeds tend to remain "puppy-like" in temperament longer — a 2-year-old Great Dane may still exhibit adolescent impulsivity.
- Coat maturation: Many breeds transition from puppy coat to adult coat between 6–14 months. Double-coated breeds (Huskies, German Shepherds) may not develop their full adult coat density until 2–3 years.
- Brain development: The canine prefrontal cortex (responsible for impulse control and decision-making) continues developing until approximately 12–18 months, which explains why adolescent dogs (6–18 months) often seem to "forget" previously learned commands.
Frequently Asked Questions
At what age do dogs stop growing in height?
Dogs stop growing taller when their growth plates close. For toy breeds, this happens around 6–8 months. Medium breeds stop around 10–12 months. Large breeds finish at 14–18 months, and giant breeds may continue growing in height until 18–24 months. Your vet can confirm growth plate closure with a simple X-ray.
Do dogs stop growing at 6 months?
Only the smallest toy breeds (under 10 lb / 4.5 kg) approach full height by 6 months. Most dogs at 6 months have reached roughly 60–75% of their adult height and still have significant growing to do. This is a common age for growth spurts in medium and large breeds.
Can a dog still grow after being spayed or neutered?
Yes. In fact, early spay/neuter (before growth plates close) may allow a dog to grow slightly taller than they would have otherwise, because sex hormones are responsible for signaling growth plate closure. The difference is usually minor (a few millimeters to a centimeter in long bones) but can affect joint angles in predisposed breeds.
How can I predict my mixed-breed puppy's adult size?
For mixed-breed puppies, adult weight estimation is imprecise. A common formula used by veterinarians: weight at 16 weeks × 2 = approximate adult weight for medium breeds. For large breeds, weight at 6 months × 2 is more accurate. DNA testing (such as the Embark or Wisdom Panel breed identification tests, typically $99–$199) can identify breed composition and give you a better size estimate based on the breeds detected.
Is it normal for my puppy to seem skinny during growth?
Yes, many puppies go through a "lanky" phase between 4–8 months where they appear thin despite eating well. This is especially common in sighthounds, herding breeds, and any dog going through a rapid growth spurt. As long as your puppy is eating a complete and balanced diet, maintaining energy levels, and following a reasonable weight curve (your vet tracks this at wellness visits), a lean appearance during peak growth is typically normal. A body condition score (BCS) of 4–5 out of 9 is ideal for growing puppies.
Why do giant breed dogs take so long to grow?
Giant breeds must build a skeletal frame that may be 40–50 times larger than a toy breed's, starting from a similarly sized embryo. Their growth plates remain active longer to allow sufficient cartilage proliferation and bone mineralization. Rushing this process — through overfeeding or excessive calcium supplementation — can actually cause skeletal deformities. The extended growth period is a biological necessity for building a structurally sound large frame.
References
- Salt, C., Morris, P.J., German, A.J. et al. "Growth curves for dogs of different breeds and sizes." Journal of Veterinary Internal Medicine, 2020.
- Hart, B.L., Hart, L.A., Thigpen, A.P. et al. "Assisting decision-making on age of neutering and associated health risks." Frontiers in Veterinary Science, 2020.
- Sutter, N.B., Bustamante, C.D., Chase, K. et al. "A single IGF1 allele is a major determinant of small size in dogs." Science, 316(5828):1122-1125, 2007.
- Merck Veterinary Manual: Feeding Growing Dogs
- AKC: Understanding Puppy Growth Rates
Anouk Beaumont
All our authors care for dogs every day — read more of their work on the authors page.
