When Do Puppies Stop Growing? A Size-by-Size Timeline

Most puppies finish growing between six months and two years, and adult size decides where in that window yours lands. So the useful question is not how old your puppy is but how big it will be, and this guide is organised that way. It belongs to the puppy stage, where most of the growing happens.

The growth timeline by adult weight

The American Kennel Club publishes a puppy growth chart by percentage of adult size, split into four adult-weight classes. AKC marks every figure as approximate.

At six months an extra-large puppy is about half grown, while a small dog is three-quarters of the way there.

Rule of thumb: The bigger the adult, the longer the growth, and the smaller the share that is finished on any given birthday.

When each size is done: what vets say

AKC and VCA Animal Hospitals give ranges, and they overlap because "stops growing", "adult size" and "adulthood" are different finish lines.

AAHA ends the puppy stage when rapid growth stops, around six to nine months depending on breed and size; slower growth continues past it. The dog age calculator gives your dog's stage alongside its age.

Taller, heavier, finished: three separate finish lines

Height stops when the growth plates close

The long bones of the legs grow from growth plates, soft zones that make new tissue through puppyhood. Dr. Jerry Klein, AKC's chief veterinarian, explains that once they stop producing tissue and fully calcify, they have closed and the bone is at its final size. AKC's rough line is that most puppies stop getting taller by 12 months, while large and giant breeds may keep developing to 18 to 24 months.

A rib check for mixed breeds

Dr. Klein's tip for a dog of unknown heritage: run your hands down the rib cage. If you can still feel the knobs of the ribs, which are growth plates, the dog will probably keep growing in height.

Filling out comes last

After skeletal growth ends, AKC notes that young dogs keep developing muscle and body fat. Regular weigh-ins plus body condition checks, which VCA recommends throughout growth, tell healthy filling out from surplus.

Height ends when the growth plates close; weight and muscle keep changing after that, which is why the scale stays useful.

How big will my puppy get?

No formula guarantees an adult weight. The growth-chart method from the WALTHAM Petcare Science Institute and Royal Canin Academy starts from an estimate and lets the puppy correct it:

1. Start from the best estimate you have. The breed's expected adult weight, or the parents' weights if they are in ideal body condition, per Royal Canin Academy.
2. Pick the matching chart. WALTHAM publishes 14 growth charts, male and female across seven size groups, validated from 12 weeks of age.
3. Weigh often. Royal Canin Academy suggests every two weeks at minimum and weekly at best, at the same time of day.
4. Let the curve correct you. A few plotted weights show which percentile line the puppy follows, and WALTHAM says you can switch charts if the first size guess was wrong.

The limits:

• Mixed breeds start as a best guess, then get placed by their first recorded weights.
• Giant breeds resist a single curve. The 2017 PLOS ONE study that built these growth standards could not fit one curve to giant breeds, because Great Danes and Mastiffs grew differently from each other. VCA tells giant-breed owners to ask their vet for an appropriate curve.
• A percentile is not a grade. Royal Canin Academy reports that healthy dogs rarely leave their original percentile line, while dogs obese by age three had usually crossed two or more.

Then buy for the estimate. The crate size tool sizes a crate to the adult dog; the puppy crate size guide explains why its pick, the MidWest iCrate Double Door, comes with a divider. A first collar should adjust too, like the five-setting Mighty Paw Leather Collar.

What the timeline changes about food

VCA's nutrition pages turn the timeline into a feeding plan:

• Faster is not better. VCA says maximal growth, usually from overfeeding or free-choice feeding, raises the risk of skeletal deformities and obesity, and recommends measured portions.
• Large and giant puppies are the sensitive group. VCA counts dogs that reach 70 lb or more as adults as large or giant, and says they need calcium and phosphorus in more tightly controlled amounts. Look for an AAFCO statement for growth "including the growth of large size dogs (70 lb or more as an adult)".
• No add-ons. Puppies need more calcium than adults, but VCA warns that excess calcium can contribute to growth abnormalities, and says to give no vitamin or mineral supplements on top of a complete puppy food without asking your vet.

On the puppy food shelf, Royal Canin Large Puppy is our pick for a puppy heading to 56 to 100 pounds, and Blue Buffalo Life Protection Puppy for small and medium puppies. Check any bag's AAFCO statement against your puppy's expected adult size.

When to switch a puppy to adult food

Switch when your puppy is mature, not on a birthday. VCA says veterinary nutritionists recommend the move to adult food once a dog has reached maturity, which it defines as 80 to 90 percent of predicted adult size. So puppies eat puppy food for anywhere from about six months to two years, depending on expected adult weight:

Purina groups large and giant dogs together and VCA gives no pound cutoffs, so the rows are our alignment. Where they disagree, as for small dogs, ask your vet rather than splitting the difference.

Make the change over 7 to 14 days, per VCA: roughly 90 percent puppy food and 10 percent adult on day one, 80 and 20 on day two, and so on. Purina's guide allows 7 to 10 days and notes that feeding puppy food past maturity can lead to excess weight.

Exercise while the growth plates are open

AKC advises regular, moderate exercise for growing puppies. Dr. Klein says road work or jogging is never recommended for a dog under 14 to 18 months, especially large and giant breeds, until the growth plates have fused.

Rule of thumb: Short walks on softer ground such as grass for now, and no running-partner plans before 14 to 18 months.

Big dogs are still growing through our adolescent stage, so supervised play in a tall pen like the VISCOO 40-Inch Playpen fits AKC's moderate-exercise advice better than distance does.

When to take the growth question to your vet

Bring your weight log, and go sooner for:

• Limping, stiffness or reluctance to move, especially in a large or giant puppy. VCA lists hip and elbow dysplasia and osteochondrosis among the developmental orthopedic diseases those breeds are predisposed to.
• A puppy crossing percentile lines on its chart, up or down.

The size timeline tells you roughly when. Your puppy's own curve tells you whether.