Puppy Growth Calculator
How big will your puppy get? Enter its age and what it weighs today and get a predicted adult weight, plus the weight to expect at every weigh-in between now and full size. No breed needed — it works for mixed breeds too.
Skip it if you have no idea — the size is guessed from the age and weight.
Predictions come from typical growth curves for each size class, not from your individual puppy's genetics. Neutering age, diet and the size of both parents all move the final number — ask your vet if the answer looks far off what you expected.
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How the prediction is made
Puppies do not grow at a steady rate, but they do grow at a predictable one. By six months a Chihuahua is nearly three-quarters of its final weight, while a Great Dane is under half — which is why any calculator that treats all puppies the same is useless for the breeds people most want to ask about.
This one starts from the share of adult weight a puppy of a given size class has typically reached at a given age, then divides:
adult weight = current weight ÷ share of adult weight reached
A five-month Labrador at 16 kg is about 42% grown, so it projects to roughly 39 kg. The same 16 kg on a five-month Beagle, already 55% grown, projects to about 29 kg — a very large Beagle, and a sign to check the breed.
The shares come from the same growth curves used to build every breed weight chart on this site, so a prediction here will never contradict the chart on your breed's page.
How much of its adult weight a puppy has reached
The table the calculator runs on. Read across to see how much growing is left at each age — and how differently the size classes behave.
| Size class | 2 mo | 3 mo | 4 mo | 6 mo | 9 mo | 12 mo | Fully grown |
|---|---|---|---|---|---|---|---|
| Toy | 20% | 33% | 45% | 72% | 92% | 100% | 10–12 months |
| Small | 17% | 30% | 42% | 68% | 88% | 100% | 12 months |
| Medium | 13% | 25% | 36% | 60% | 82% | 95% | 12–18 months |
| Large | 11% | 21% | 31% | 52% | 72% | 87% | 18–24 months |
| Giant | 9% | 18% | 26% | 45% | 63% | 78% | 24 months |
These are typical figures for each size class, not a breed standard. Individual puppies run ahead of or behind the curve and still finish in a normal place.
You know the numbers. Now watch the trend.
A single weigh-in tells you very little — a chart of the last six months tells you everything. PetNoter keeps your puppy's weight history in one place, free.
- Log a weigh-in in seconds and see the trend line
- Reminders for weigh-ins, vaccinations and vet visits
- Vet records, prescriptions and photos stored per pet
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How much to trust the number
The prediction is a division, and dividing by a small number magnifies whatever error is in it. That single fact explains most of what you need to know about accuracy:
- Under 12 weeks: broad. A large-breed puppy is under 20% grown and a giant breed under 16%, so the curve being slightly off, or the puppy having just eaten, moves the answer by kilos.
- Four to six months: the sweet spot. Enough growth has happened to be informative, and for a purebred dog the prediction is usually within about 10–15% of the finished weight.
- Nine months and up: close. Most of the growing is done and the remaining change is muscle filling out rather than frame.
- Mixed breeds: wider than purebreds at every age, because the size class itself is an assumption rather than a known fact.
- Overweight puppies read high. The calculator cannot tell fat from frame. A chubby puppy projects to a larger adult than it will actually be — and carrying extra weight while the joints are still forming is its own problem, particularly in large breeds.
The honest use of a prediction is as a plan to check against, not a target to feed towards. Weigh every one to two weeks while your puppy is growing and watch whether it tracks its own curve — a puppy that suddenly leaves the line it has been following is worth a vet's attention, whichever direction it goes.
Frequently Asked Questions
How does the puppy growth calculator work?
It works backwards from a growth curve. Puppies reach a predictable share of their adult weight at each age — a large-breed puppy is around half grown at six months, a toy breed nearly three-quarters — so dividing the current weight by that share gives the adult weight. Enter your puppy's age and what it weighs today, and the calculator returns a predicted adult range plus the weight to expect at every age between now and full size.
How big will my puppy get?
For a purebred puppy the breed's adult range is the strongest guide, and the calculator checks your prediction against it. For a mixed breed, the puppy's own current weight is the better signal — enter the age and weight and the calculator will work out which size class the numbers fit, then project from there.
How accurate is a puppy weight prediction?
Accuracy improves sharply with age. Between four and six months, a prediction is usually within about 10–15% of the final weight for a purebred dog. At eight to ten weeks it is much rougher, because the calculation divides by a small number and multiplies any error along with it. That is why the calculator returns a range rather than a single figure, and why the range narrows as your puppy grows.
Why won't it predict for a puppy under eight weeks?
Because the answer would not be worth having. A puppy under eight weeks is typically still nursing, its weight moves noticeably with the last feed, and it has reached under a tenth of its adult weight — so a 100 gram measurement error can shift the predicted adult weight by kilos. Weigh again at eight weeks.
Does the calculator work for mixed-breed puppies?
Yes, and it is the more useful case. Leave the breed field empty and the calculator infers a size class from the age and weight you enter, by testing which growth curve produces an adult weight consistent with that class. If you know roughly how big the parents were, picking the expected adult size directly will be closer still.
When do puppies stop growing?
Toy and small breeds are usually finished by 10–12 months. Medium breeds fill out until 12–18 months. Large breeds keep growing until 18–24 months, and giant breeds until around two years, adding muscle and chest depth long after they have reached full height.
Does neutering change how big a puppy gets?
It can. Neutering before the growth plates close tends to delay their closure, which often produces a slightly taller dog than the same puppy would have been otherwise. The effect on weight is smaller than the effect of diet, and it is not captured by any growth curve — discuss timing with your vet, especially for large and giant breeds.
Related tools
Check whether your dog is a healthy weight for its breed →
Track your puppy's weight in the free PetNoter app
4.8 · Free · Android & iOS