Puppy Weight Calculator: How Big Will Your Puppy Get?
Reviewed by the veterinary team at Heights Animal Hospital Updated August 24, 2026 6 min read
The short answer
- Predicted adult weight = current weight ÷ the fraction of adult weight already reached for that age and size class.
- At 16 weeks a toy puppy is about 62% of adult weight, a medium puppy about 52%, and a giant-breed puppy only about 40%.
- The popular “double the six-month weight” rule overestimates large breeds. A large-breed puppy is already about two-thirds grown at six months.
- Small dogs finish growing near 11–12 months; giant breeds are still filling out at 18–24 months.
Every puppy follows the same basic shape of growth curve (fast at first, then tapering) but the timing of that curve depends almost entirely on how big the dog will end up. That is why one multiplier cannot work for a Chihuahua and a Great Dane. The calculator below uses separate reference curves for five adult size classes, so the prediction reflects how your puppy's specific size group actually grows.
Puppy Weight Calculator
Enter today's weight, today's age and the expected size class. We work backwards from veterinary growth curves to project the adult weight.
Use weeks for accuracy under 6 months.
Not sure? Pick the class the breed (or the larger parent) belongs to. For a mixed-breed rescue, the calculator will flag if your choice conflicts with the current weight.
Predicted adult weight
–
- Still to gain
- –
- Growth finishes
- – for this size class
- Weight at 6 months
- – projected checkpoint
- Parent average
- – cross-check estimate
Projected weight checkpoints
| Age | Expected weight | % of adult |
|---|
How the puppy weight calculator works
Predicting adult weight is a division problem, not a multiplication one. If we know what percentage of their final adult weight a puppy has already reached, the rest is arithmetic:
Adult weight = current weight ÷ (percent of adult weight reached ÷ 100)
Example: a 16-week medium-breed puppy weighing 18 lb has reached about 52% of adult weight. 18 ÷ 0.52 = 34.6 lb adult.
The whole accuracy of the method rests on that percentage, and it differs sharply by size class. This is the reference table the calculator interpolates between.
Puppy weight chart: percent of adult weight by age
| Age | Toy <12 lb | Small 12–25 lb | Medium 25–50 lb | Large 50–100 lb | Giant 100+ lb |
|---|---|---|---|---|---|
| 8 weeks | 29% | 25% | 22% | 19% | 16% |
| 12 weeks (3 mo) | 47% | 42% | 38% | 33% | 28% |
| 16 weeks (4 mo) | 62% | 57% | 52% | 46% | 40% |
| 20 weeks (5 mo) | 74% | 69% | 64% | 57% | 50% |
| 24 weeks (6 mo) | 84% | 79% | 74% | 67% | 59% |
| 32 weeks (7.5 mo) | 95% | 91% | 87% | 81% | 73% |
| 40 weeks (9 mo) | 99% | 97% | 94% | 90% | 84% |
| 52 weeks (12 mo) | 100% | 100% | 99% | 97% | 94% |
| 18 months | 100% | 100% | 100% | 100% | 98% |
| 24 months | 100% | 100% | 100% | 100% | 100% |
The quick multipliers that actually match the data
If you want a mental shortcut rather than a calculator, these are the multipliers implied by the table above, and they are noticeably different from the folk rules you will see repeated online.
| Size class | × weight at 12 weeks | × weight at 6 months |
|---|---|---|
| Toy | × 2.1 | × 1.2 |
| Small | × 2.4 | × 1.3 |
| Medium | × 2.6 | × 1.35 |
| Large | × 3.0 | × 1.5 |
| Giant | × 3.6 | × 1.7 |
Notice that the widely repeated rule “double your puppy's six-month weight” is only close for giant breeds, and it overshoots badly for everything smaller. A Labrador at six months is already roughly two-thirds of the way to adult weight, not halfway.
When do puppies stop growing?
Two things stop at different times, and confusing them is the most common mistake owners make. Height stops when the growth plates close. Weight keeps climbing for months afterwards as the chest fills out and muscle matures.
| Size class | Height finished | Weight finished | Growth plates closed |
|---|---|---|---|
| Toy | 6–8 months | ~11 months | 8–11 months |
| Small | 8–10 months | ~12 months | 10–12 months |
| Medium | 10–12 months | ~14 months | 12–14 months |
| Large | 12–16 months | ~17 months | 14–18 months |
| Giant | 16–20 months | ~22 months | 18–24 months |
Growth-plate timing is also why spay and neuter timing is now discussed breed by breed rather than applied as a blanket rule: in several large breeds, removing sex hormones before the plates close is associated with a higher rate of certain joint disorders. It is a conversation worth having at your puppy's four-month visit.
Feeding a growing puppy without overshooting
The goal of puppy nutrition is not maximum growth. It is steady growth along the curve. Three rules matter more than brand choice:
Use a growth-labelled diet
The bag must carry an AAFCO statement for growth. For puppies expected to exceed 70 lb, it must specifically say it is suitable for large-size growth, which caps calcium.
Never add calcium
Supplementing calcium on top of a complete puppy diet is a documented cause of skeletal disease in large breeds. The diet is already balanced.
Feed to the body, not the bag
Bag guidelines are population averages. Adjust so you can feel ribs easily under a thin fat cover and see a waist from above.
Meals per day
Three to four meals daily until about 4 months, then three until 6 months, then twice daily for life. Toy breeds need more frequent meals to avoid low blood sugar.
Growth problems worth a phone call
Your puppy is not gaining weight week to week • is losing weight • has a pot-bellied look with a thin body (a classic parasite picture) • is dramatically smaller than littermates • is limping, sitting oddly or reluctant to exercise • has a giant-breed frame that is growing far faster than the curve • has persistent diarrhoea or a poor coat.
Weigh your puppy at the same time each week during the first six months. A steady climb is reassuring; a flat week or a drop is the earliest and clearest sign that something is wrong, and it shows up long before a puppy looks unwell.
Frequently asked questions
How big will my puppy get?
Divide your puppy's current weight by the fraction of adult weight typical for their age and size class. At 16 weeks that fraction is about 62% for a toy breed, 52% for a medium breed and 40% for a giant breed. A 16-week medium-breed puppy weighing 18 lb therefore projects to roughly 34–35 lb as an adult. The calculator on this page runs the full interpolated curve and gives you a likely range rather than a single number.
How accurate is a puppy weight calculator?
For a purebred puppy of known breed, expect the prediction to land within about 10% of the true adult weight most of the time. For mixed-breed puppies of unknown parentage, accuracy is lower because the size class itself is a guess. Accuracy improves considerably after 16 weeks, once the fastest and most variable phase of growth is behind them.
Is it true you double a puppy's weight at 6 months?
Only for giant breeds, roughly. The multiplier that matches real growth data is about 1.2 for toy breeds, 1.3 for small, 1.35 for medium, 1.5 for large and 1.7 for giant. Applying ×2 to a Labrador at six months would predict a 90–100 lb adult when the true figure is usually 65–75 lb.
At what age do puppies stop growing?
Small and toy breeds are essentially done by 10–12 months. Medium breeds finish around 12–14 months. Large breeds keep filling out to 15–18 months, and giant breeds are not fully mature until 18–24 months. Height stops before weight does, so a dog that looks full-height at a year old may still add 5–10% more body weight.
Can I predict adult weight from the parents?
For purebred puppies, yes, and it is often the single best predictor: adult weight tends to fall near the average of the two parents, with males trending toward the larger parent and females toward the smaller. It fails for mixed-breed litters, where puppies can fall anywhere between the two parental sizes or, occasionally, outside that range. The calculator lets you enter both parents so you can compare the two methods.
Does paw size predict how big a puppy will get?
Loosely, and only as a directional hint. Large paws relative to the body suggest more frame still to fill, which is why the observation persists. It is far less reliable than a weight-and-age calculation, and it fails completely in breeds bred for heavy bone such as Basset Hounds. Use the growth curve; treat the paws as a curiosity.
My puppy is growing faster than the chart. Is that good?
Not in a large or giant breed. Rapid growth is one of the recognised risk factors for developmental orthopaedic disease, including hip dysplasia, osteochondrosis and hypertrophic osteodystrophy. Excess calories and excess calcium both contribute. Feed a diet formulated for large-breed growth, avoid all calcium supplements, and keep your puppy lean rather than well-covered. In small breeds, running above the curve usually just means the size class was underestimated.
How often should I weigh my puppy?
Once a week for the first six months, at the same time of day, on the same scale. Small puppies can be weighed by holding them on a bathroom scale and subtracting your own weight. Plot the numbers: the shape of the line tells you more than any single reading, and a plateau or a drop is a reason to call your veterinarian.
Is your puppy growing the way they should?
Heights Animal Hospital in Jackson Heights, NY provides wellness exams, diagnostics, surgery and urgent care. A calculator is a starting point. An exam is the answer.
References
- Hawthorne AJ, Booles D, Nugent PA, Gettinby G, Wilkinson J. “Body-weight changes during growth in puppies of different breeds.” Journal of Nutrition 2004;134(8):2027S-2030S. (Waltham growth data)
- German AJ, Woods GRT, Holden SL, et al. Puppy growth standards and the WSAVA Global Nutrition Committee puppy growth charts. wsava.org.
- Salt C, Morris PJ, German AJ, et al. “Growth standard charts for monitoring bodyweight in dogs of different sizes.” PLoS ONE 2017;12(9):e0182064.
- Association of American Feed Control Officials (AAFCO). Dog Food Nutrient Profiles for Growth. aafco.org.
- American Animal Hospital Association. “2019 AAHA Canine Life Stage Guidelines.” aaha.org.