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.
The short version, from our own growth model: a puppy is around 40–45% of its adult weight at three months and 63–77% at six, with the smaller dog further along at every age. Our full percentage-of-adult-weight chart, by size class gives the figure for each month from three to eighteen, and explains how to use it on a puppy whose breed you do not know.
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 15 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, or 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) carries more risk while those plates are still open. So if you have a large-breed puppy and want to know when it is safe to start running with them, the front-leg plates are the ones to ask your vet about. Before that appointment, it is worth knowing what the exercise cohort evidence actually measured. The much-repeated “five minutes per month of age” rule has no traceable source at all.
These ranges are wide because they pool dogs of different sizes. Only a radiograph tells you about your own 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?
Short answer: it does not stunt growth, and if anything it produces a slightly taller, longer-limbed dog.
This gets handled badly nearly everywhere, and the reason is that two separate findings get blurred together. One is about bodyweight. The other is about bone length. Different studies measured them, and they point in different directions.
On weight, the effect is under one centile: less than one line on a growth chart, where nine lines cover the whole healthy range. The charts are validated for neutered and intact dogs alike. On bone length, the hormones that trigger the growth plates to close are the ones surgery removes. Take them away early and the long bones keep growing a little longer.
Either way the effect is too small to be a good reason on its own to time the surgery. Joint health and behaviour are what actually matter, and they are a conversation for your vet. We set out what the two neutering studies each measured, and the four questions worth taking to that appointment.
The paw-size myth
Nobody has tested it. There is no published study linking a puppy’s paw size to its adult size, though the observation behind the rule is real, because the paw’s growth plates close months before the leg’s do. Every puppy looks big-footed for a while. We take that apart properly in do big paws mean a big dog?.
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. Paw size has never been measured against it.
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.
So a mix is not harder to time than a purebred. It is only harder to size, and that is a separate question with its own ranked set of methods: parents’ weights first, then a DNA test, then the puppy’s own curve from about 16 weeks. We work through how to estimate a mixed-breed puppy’s adult size, including the case where the parents are unknown.
One caveat worth stating plainly here, because it applies to every number on this page: 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 hold calcium and calories to a set ceiling. Too much calcium and fast growth during puppyhood are both linked to developmental orthopedic disease (joint and bone problems that start while the dog is still growing) in large breeds. If your puppy will finish over about 50 lb, a large-breed puppy food is the safer default. The AAFCO labelling threshold sits higher, at 70 lb. And what the large-breed label actually guarantees is a calcium ceiling rather than a lower calcium level. The minimum is identical.
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
Truly stunted growth is uncommon. It does have causes worth ruling out, and most of them are more treatable the earlier they are caught.
- Intestinal parasites, which steal nutrition and are very common in puppies.
- Poor or badly balanced feeding, including some home-prepared diets.
- Portosystemic shunt: a blood vessel, present from birth, that carries blood past the liver. It shows up classically as a puppy failing to thrive alongside signs of brain trouble.
- Juvenile hypothyroidism, an underactive thyroid gland in a young dog, and other hormone conditions. All are rare.
- Long-running illness of almost any kind, which pulls energy away from growth.
A single low weight reading means very little. What is worth a vet visit is a puppy that has stopped gaining for several weeks while still young, or one falling steadily away from the line it was tracking.
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. A centile is a rank: a puppy on the 25th centile is lighter than three puppies in four of its age and size. The WALTHAM charts are free, sex-specific and used in clinics. What matters is not which line your puppy sits on, but whether it stays on roughly the same one. A puppy steadily climbing across the lines 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. Fast growth carries real joint risks in large breeds.
- Limping, stiffness, or reluctance to put weight on a leg during a growth spurt.
- A puppy well below the size of its littermates.
Stunted growth has causes that are treatable when caught early. Intestinal parasites, poor feeding and conditions present from birth, such as portosystemic shunts, are the main ones.