Ask three sources when puppies stop growing and you will get three different answers. That is not because anyone is being careless. It is because “fully grown” describes three separate events that happen months apart, and most articles quietly pick one without telling you which.
Sorting that out is most of the answer.
The three milestones people confuse
When an owner asks whether their puppy is done growing, they usually mean one of these — and the honest answer depends on which.
| Milestone | What it means | When |
|---|---|---|
| Adult weight reached | The number on the scale stops climbing | 9–15 months for most dogs |
| Growth plates close | Bones stop lengthening. Final height is set. | ~12 months typical; 18–20 months in giant breeds |
| Physically mature | Chest deepens, muscle fills out, the adult shape settles | 12 months in small breeds; up to 24 in giants |
A Great Dane can reach its adult weight at 15 months, close its growth plates at 18, and still be visibly changing shape at two years. All three statements are true simultaneously. Most confusion about puppy growth dissolves once you know which one is being described.
The practical version: weight tells you when to switch off puppy food; growth plates tell you when high-impact exercise is safe. They are not the same date, and the second one matters more for your dog’s joints.
When puppies stop growing, by size
The Purina Institute publishes the most commonly used windows, based on adult weight rather than breed:
| Size class | Adult weight | Growth typically complete |
|---|---|---|
| Toy | Under 12 lb (6 kg) | 6–9 months |
| Small | 13–20 lb (6–10 kg) | 8–10 months |
| Medium | 20–50 lb (10–25 kg) | Up to 12 months |
| Large | 50–100 lb (25–45 kg) | 12–18 months |
| Giant | Over 100 lb (45 kg) | Up to 24 months |
The pattern is consistent across every source: bigger dogs grow for longer. A study of twelve breeds published in the Journal of Nutrition found exactly this — larger breeds have a longer growth period, not merely a faster one.
Adult weight usually arrives earlier than the table suggests. Veterinary nutrition texts put toy, small and medium breeds at adult weight by around 9–10 months, and large and giant breeds at 11–15 months, with full physical maturity following months later.
How much of its adult size is your puppy now?
Growth is fastest early and then flattens, which is why a puppy that doubled in a month can look like it has stalled by nine months. It has not — it is on the flat part of the curve.
These figures come from our own growth model, fitted to published breed growth charts spanning Chihuahua to Great Dane. The full methodology and its error margins are published.
| Age | Toy (6 lb) | Small (16 lb) | Medium (35 lb) | Large (70 lb) | Giant (130 lb) |
|---|---|---|---|---|---|
| 3 months | 45% | 40% | 35% | 32% | 29% |
| 4 months | 58% | 52% | 48% | 44% | 41% |
| 6 months | 77% | 73% | 69% | 66% | 63% |
| 9 months | 92% | 89% | 88% | 86% | 84% |
| 12 months | 97% | 96% | 95% | 94% | 94% |
| 18 months | 100% | 100% | 99% | 99% | 99% |
Two things worth noticing. Bigger dogs are a smaller fraction of their adult weight at every age — a giant-breed puppy at four months has done less of its growing than a toy at the same age. And the halfway point moves later with size: a toy breed passes 50% of adult weight at around 14 weeks, a giant not until about 21.
That second point is why the popular rule of thumb — “double the weight at 16 weeks” — is roughly right for a medium breed and meaningfully wrong for everything else.
Why the advice you find online disagrees with itself
If those numbers do not match what you read elsewhere, you are not imagining it. Here is the same question answered by four well-known sources:
| Source | “Medium” defined as | Growth complete |
|---|---|---|
| AKC | 21–50 lb | ~12 months |
| PetMD | 24–59 lb | 12–15 months |
| Diamond Pet | not specified | 9–12 months |
| Dogster | not specified | 15 months |
They disagree by six months, and they disagree about what “medium” even means. Neither is an error exactly — they are drawing on different reference sources with different cut-offs, and none of them says so.
Use adult weight, not the size label. The label is a summary of the weight; going straight to the weight skips a layer of ambiguity. If you do not know your puppy’s likely adult weight, our puppy size calculator estimates it from your dog’s current weight, age and breed.
Growth plates: which ones close, and when
Growth plates — physes — are bands of cartilage near the ends of long bones where lengthening happens. When they ossify, the bone can no longer get longer, and your dog’s height is fixed.
Every article says “growth plates close around a year.” Few say which plates, or that they do not close together. From standard veterinary radiography references:
| Growth plate | Typical closure |
|---|---|
| Distal humeral condyles | 6–8 months |
| Olecranon (elbow point) | 6–10 months |
| Distal ulna | 7–12 months |
| Femoral head | 8–12 months |
| Proximal tibia | 8–12 months |
| Distal radius (just above the wrist) | 6–12 months |
| Proximal humerus (shoulder) | 10–13 months |
The last plates to close in most dogs are the distal radius and ulna and the proximal humerus — the front legs, roughly 10–13 months. In very large and giant breeds they can stay open until 18–20 months.
This is the number that matters for exercise. Repeated high-impact activity — long runs on hard surfaces, jumping down from heights, agility work — is a greater risk while those plates are still open. If you have a large-breed puppy and are wondering when it is safe to start running with them, the front-leg plates are the ones to ask your vet about.
Ranges are wide because they pool dogs of different sizes. Only a radiograph tells you about your individual dog.
Giant breeds: the honest answer is that nobody knows precisely
Owners of giant-breed puppies get the vaguest advice, and there is a real reason.
The best evidence base available is Salt et al. (2017), which built veterinary growth standard charts from over six million weight records. It produced validated centile curves for five size categories — and then stopped. In the authors’ own words:
The most common breeds in size category VI (e.g. Great Dane, Mastiff and Rottweiler) had widely varying growth trajectories and, consequently, it was not possible to create a growth curve model for this category.
And plainly: “they do not apply dogs with an adult weight >40 kg.”
No validated growth chart exists for dogs over 88 lb. The dogs whose owners worry most about growth are precisely the ones the science declines to model, because a Great Dane and a Mastiff do not grow alike even though both are “giant.”
The WALTHAM growth charts built on that study reflect it: the chart for dogs under 6.5 kg runs to 55 weeks, and they extend progressively to 75 weeks for 30–40 kg dogs. Past 40 kg there is no chart to run.
You will also see “giant breeds grow until three years old.” There is no peer-reviewed basis for that figure. What is true is that weight gain continues well past skeletal closure in giant breeds as the chest deepens and muscle develops — which is almost certainly where the folklore comes from. The bones have stopped; the dog has not finished changing.
Does neutering change how big my dog gets?
This is handled badly nearly everywhere, because two different findings get blurred together.
On weight, the effect is small. Salt et al. found that neutering produced slight shifts in growth trajectory — upward if done before 37 weeks, downward after — but the shifts were under one centile and never large enough to cross neighbouring centile lines. The growth charts are validated for neutered and intact dogs alike.
On height, the effect is real and goes the opposite way to what most people expect. Growth plate closure is triggered in part by gonadal hormones. Remove the source of those hormones before the plates close and closure is delayed, so the long bones keep lengthening slightly longer. As Today’s Veterinary Practice summarises the orthopedic literature, gonadectomy before physeal closure “is associated with significantly greater final length of associated long bones.” The foundational study is Salmeri et al. (1991).
So: early neutering does not stunt growth. If anything it produces a slightly taller, longer-limbed dog. The effect is modest, and it is not a good reason on its own to time the surgery one way or the other. Joint health and behaviour are the considerations that actually matter, and they are a conversation for your vet.
The paw-size myth
Big paws do not mean a big dog.
This is repeated constantly and has no published evidence behind it. Reputable sources cannot even agree whether the pattern holds loosely, which is what you would expect from an observation that was never measured properly. Some breeds are simply built with heavy bone and large feet.
What actually predicts adult size, in order: the breed’s typical adult weight, the parents’ adult weights, and your puppy’s own growth curve so far. All three are measurable. Paws are not.
Mixed breeds: use the weight, not the label
Growth timing tracks adult size, not ancestry. A 30 lb mixed breed finishes on roughly the same schedule as a 30 lb purebred, so the practical problem is estimating the adult weight in the first place.
In order of reliability:
- The parents’ adult weights, if known. Average them. A puppy rarely finishes much heavier than its larger parent.
- A DNA test, which gives breed proportions and, in most cases, a predicted adult weight.
- The puppy’s own growth curve, which becomes genuinely informative from about 16 weeks onward.
One caveat worth stating plainly: the veterinary growth standards were built on purebred populations and have never been validated on mixes. Estimates for a mixed-breed puppy of unknown parentage carry real uncertainty, and anyone presenting one as a precise figure is overselling it.
Does my puppy still grow after one year?
Often, yes — and this is where “my vet said he’s full grown but he keeps getting bigger” comes from.
By twelve months most dogs are at roughly 94–97% of adult weight. That remaining few percent arrives slowly over the following months. In large and giant breeds, the shape change after twelve months is more noticeable than the weight change: the chest drops and widens, the head broadens, and the leggy adolescent proportions resolve into an adult outline.
So a Labrador at fourteen months may be its final height with several more pounds of frame to come. A Great Dane at eighteen months may have closed its growth plates and still look unfinished.
Height stops first. Substance follows.
Feeding a growing puppy
Two things matter more than brand choice.
Large-breed puppy formulas exist for a reason. They are formulated with controlled calcium and energy density, because excessive calcium intake and rapid growth during the puppy phase are associated with developmental orthopedic disease in large breeds. If your puppy will finish over about 50 lb, a large-breed puppy food is the safer default.
Faster is not better. It is tempting to read a heavier puppy as a healthier one, but rapid growth is a joint risk in big dogs, not an achievement. Research following dogs to age three found that consistently crossing upward through weight centiles from around six months was an early signal of later weight problems. Steady tracking along the same centile is what you want to see.
Switch off puppy food when growth has finished — earlier for small breeds, later for large — which is a question of adult weight, and worth confirming with your vet rather than guessing from a bag.
What can stop a puppy growing properly
Genuinely stunted growth is uncommon, but it has causes worth ruling out, most of them more treatable the earlier they are caught:
- Intestinal parasites, which divert nutrition and are very common in puppies
- Inadequate or poorly balanced nutrition, including some home-prepared diets
- Portosystemic shunt, a congenital vascular abnormality that classically presents as a puppy failing to thrive alongside neurological signs
- Juvenile hypothyroidism and other endocrine conditions, which are rare
- Chronic illness of almost any kind, which diverts energy from growth
A single low weight reading means very little. A puppy that has stopped gaining for several weeks while still young, or is falling steadily away from where it was tracking, is worth a vet visit.
How to tell whether your puppy has finished growing
- Weigh regularly. Every two weeks, same scale, ideally same time of day. A trend beats a single reading.
- Look for a flat line. Six to eight weeks with no meaningful gain, in a dog past the typical age for its size, means growth has finished.
- Watch shape, not just weight. If the scale is steady but the chest is still deepening, your dog is maturing rather than growing.
- Ask for a radiograph if it matters. If you need a definite answer — usually for exercise or surgical planning — an X-ray shows growth plate status directly. Nothing else does.
- Track against a centile chart. The WALTHAM charts are free, sex-specific and used clinically. What matters is not which line your puppy sits on, but whether it stays on roughly the same one. A puppy steadily climbing across centiles is the pattern worth mentioning to your vet.
When to talk to your vet
Growth is one of the more reliable early signals that something is wrong. Worth raising if you see:
- A puppy that has not gained weight in several weeks while still young
- Weight climbing much faster than expected for the breed — rapid growth carries real joint risks in large breeds
- Limping, stiffness, or reluctance to bear weight during a growth spurt
- A puppy well below the size of its littermates
Stunted growth has causes that are treatable when caught early, including intestinal parasites, inadequate nutrition and congenital conditions such as portosystemic shunts.