Puppy Weight Calculator
Estimate how big your puppy will be when fully grown, from their current weight, age and expected adult size.
Your puppy's estimated adult weight
Estimate only. Mixed breeds and fast or slow growers can land outside the range.
Puppy Growth Chart: Percent of Adult Weight by Age
The calculator divides your puppy's weight by the share of adult weight a puppy of that size usually reaches at that age.
| Age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 2 months | 28% | 19% | 14% | 12% |
| 3 months | 42% | 29% | 22% | 18% |
| 4 months | 56% | 39% | 31% | 26% |
| 5 months | 68% | 49% | 40% | 34% |
| 6 months | 78% | 58% | 50% | 42% |
| 8 months | 90% | 75% | 66% | 57% |
| 10 months | 96% | 87% | 78% | 69% |
| 12 months | 100% | 95% | 86% | 78% |
| 15 months | 100% | 100% | 95% | 88% |
| 18 months | 100% | 100% | 100% | 95% |
How the puppy weight calculator works
Puppies grow fastest in the first months, and small breeds finish growing much sooner than large ones. A small dog reaches about 78% of its adult weight by 6 months and is fully grown at about 12 months, while a giant breed is only around 42% grown at 6 months and keeps filling out until about 2 years. The calculator uses an approximate growth curve for each size, finds the share of adult weight your puppy should have reached at its age, and divides your puppy's current weight by it. The quick formula is a rougher rule of thumb: weight divided by age in weeks, multiplied by 52 (the weeks in a year), which tends to work best for medium and large breeds.
FAQ
How big will my puppy get?
Enter your puppy's weight, age and expected adult size above. The calculator estimates adult weight from a growth curve for that size and gives a range of about 10% either side. Breed and the parents' sizes are the best guide to which size category to choose.
How do you predict a puppy's adult weight?
A common rule is puppy weight divided by age in weeks, multiplied by 52. A more careful method uses the share of adult weight puppies of a given size reach at each age, which is what this calculator does.
When do puppies stop growing?
Small breeds usually reach adult size by about 12 months. Medium breeds finish at 12–15 months, large breeds at 15–18 months and giant breeds at 18–24 months, although they may keep filling out slightly afterward.
How big will a 4 month old puppy get?
At 4 months a puppy has typically reached about 56% of adult weight for a small breed, 39% for medium, 31% for large and 26% for giant breeds. A medium puppy weighing 20 lb at 4 months would therefore be around 50 lb as an adult.
How big will a 6 month old puppy get?
At 6 months a puppy has typically reached about 78% of adult weight for a small breed, 58% for medium, 50% for large and 42% for giant breeds. A large-breed puppy weighing 40 lb at 6 months might be around 80 lb as an adult.
Is the 'double their weight at 6 months' rule accurate?
It is a rough rule that suits some large breeds, which are about half grown at 6 months. It overestimates for small breeds, which are closer to 80% grown, and underestimates for giant breeds.
Does paw size predict adult size?
Big paws can hint that a puppy still has growing to do, but paw size is a weak predictor on its own. Weight, age and the parents' sizes are more reliable.
How accurate is a puppy weight calculator?
It is an estimate. Mixed-breed puppies in particular can be hard to predict, so treat the result as a range and use it as a guide rather than a guarantee.
What if my puppy is above or below the curve?
Puppies grow in spurts and vary between litters, so a small gap is normal. A puppy that is much underweight, or gaining weight too fast, is worth a chat with your vet, especially for large breeds where rapid growth can strain joints.
Is this calculator veterinary advice?
No. It gives a general estimate. Your vet can give a more accurate prediction and check your puppy's growth against breed standards.
About this tool
This calculator estimates a puppy's adult weight from its current weight, age and expected size. It is a general estimate, not veterinary advice. Growth varies with breed, genetics, diet and health, so ask your vet if your puppy seems unusually small or large for its age.