Puppy Weight Calculator
Enter your puppy's current weight and age in weeks to estimate how big it will be full-grown. The estimate uses the growth-rate method: adult weight is roughly the current weight divided by the age, times 52.
How to calculate puppy weight
A puppy's average growth rate so far is its current weight divided by its age in weeks. Multiplying that rate by 52 (the weeks in a year) projects the weight at about one year old, when most dogs are close to full-grown. The method works best for medium breeds that mature around 12 months. Toy and small breeds finish growing earlier (8 to 12 months), so a very young age can read slightly high; large and giant breeds keep growing to 18 to 24 months, so an early reading can run low. For the best estimate, weigh your puppy at the checkpoint age recommended for its size and treat the result as a ±10% range.
Adult weight ≈ (current weight ÷ current age in weeks) × 52
Worked example
A puppy weighs 10 lb at 16 weeks old (about 4 months).
- Growth rate = 10 lb ÷ 16 weeks = 0.625 lb per week
- Adult weight = 0.625 × 52 = 32.5 lb
- Typical range = 32.5 × 0.9 to 32.5 × 1.1 = 29.3 to 35.8 lb
- In kilograms: 32.5 ÷ 2.205 = about 14.7 kg
Result: About 32.5 lb full-grown (roughly 29 to 36 lb, or 14.7 kg)
Frequently asked questions
How accurate is a puppy weight calculator?
It is a good ballpark, not a guarantee. The growth-rate formula is most reliable for medium breeds weighed between 14 and 22 weeks. Breed, sex, nutrition, and individual variation all shift the real adult weight, so treat the figure as a ±10% estimate rather than an exact number. Knowing the parents' adult weights is the single best predictor.
At what age is a puppy half its adult weight?
Most medium and large breeds reach about half their adult weight by 4 to 5 months, which is why an estimate around 16 weeks tends to be reasonably accurate. Small breeds hit the halfway point a little earlier and giant breeds a little later.
When do puppies stop growing?
Small breeds are usually full-grown by 8 to 12 months, medium breeds by about 12 months, and large or giant breeds keep filling out until 18 to 24 months. Because the formula projects to roughly one year, it can underestimate giant breeds; for those, weigh later (6 months or more) for a better read.
Is there a simple rule for small versus large breeds?
Two common shortcuts: for small breeds, multiply the weight at 6 weeks by 4; for large breeds, double the weight at 6 months. These rough rules and the growth-rate formula usually land within a few pounds of each other, so use whichever inputs you have on hand.
Does my puppy's weight depend on whether it is a mixed breed?
For mixed breeds, the adult size is hard to pin down because it depends on which parent's genetics dominate. The growth-rate formula sidesteps breed entirely by using the puppy's own measured growth, which makes it especially handy for rescues and mixes where the parents are unknown.