How the puppy weight calculator works
Puppies grow in a predictable curve: very fast at first, then slower, until they reach adult weight. Small breeds finish growing at around 10 to 12 months, while giant breeds keep filling out until they are about 2 years old. The calculator looks up how much of its adult weight a typical puppy of that size has reached at your puppy's age, then divides.
Worked example
A 12-week-old medium-breed puppy weighs 15 lb. Medium breeds are typically about 30% of their adult weight at 12 weeks, so the adult weight is about 15 ÷ 0.30 = 50 lb, likely between 43 and 58 lb.
Quick rules of thumb
- Toy and small breeds: about double the weight at 14 to 16 weeks.
- Medium breeds: weight at 14 weeks × 2.5 (close to our curve).
- Large breeds: about double the weight at 6 months.
- Giant breeds: double the weight at 6 months, and expect them to keep growing slowly after that.
Typical share of adult weight by age
| Age | Toy or small | Medium | Large | Giant |
|---|---|---|---|---|
| 8 weeks | 25% | 20% | 15% | 11% |
| 12 weeks | 40% | 30% | 23% | 18% |
| 16 weeks | 55% | 42% | 33% | 26% |
| 6 months | 75% | 62% | 50% | 42% |
| 9 months | 94% | 85% | 75% | 66% |
| 12 months | 100% | 96% | 89% | 81% |
| 18 months | 100% | 100% | 100% | 96% |
These are averages built from published breed growth charts. A single puppy can sit above or below the curve and still be healthy.
Other clues to adult size
- The parents. If you know the mother's and father's weights, the adult dog usually lands between them.
- Paws and legs. Big paws on a young puppy often mean more growing to do, though this is only a hint.
- Your vet. A growth check at each vaccine visit is the best way to see if your puppy is on track.
Next: work out how much to feed with the dog food calculator, or see your dog's age in human years with the dog age calculator.
Frequently asked questions
How can I tell how big my puppy will get?
Divide your puppy's weight by the share of adult weight a puppy of its size usually has at that age. A 12-week-old medium puppy is about 30% grown, so a 15 lb puppy will likely weigh about 50 lb.
At what age is a puppy half its adult weight?
Around 14 to 15 weeks for small breeds, 18 weeks for medium breeds, 6 months for large breeds and about 7 months for giant breeds.
When do puppies stop growing?
Small breeds stop at about 10 to 12 months, medium breeds at 12 to 15 months, large breeds at 15 to 18 months and giant breeds at 18 to 24 months.
Is the puppy weight calculator accurate?
It gives a reasonable estimate, usually within about 15%. Mixed breeds and puppies that were very small or large at birth can end up outside that range.
Do big paws mean a big dog?
Often, but not always. Paw size is a rough hint. The puppy's growth curve and the parents' size are better guides.
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Last updated October 2026.