Puppy Weight Calculator
Enter your puppy's current weight, age in weeks, and the size its breed finishes at. You get the size-adjusted estimate and the simple rule beside it.
8 weeks is the usual adoption age
from the breed or the parents
Estimated adult weight (size-adjusted)
41 lb
18.7 kg · uses the medium-breed growth curve
Simple rule (weight ÷ weeks × 52)
52 lb
assumes linear growth to 1 year
Worked example: 12 lb at 12 weeks
The simple rule: 12 ÷ 12 × 52 = 52 lb. The same puppy through the size-adjusted curve:
| If the breed is… | Share of adult weight at 12 wk | Estimated adult weight |
|---|---|---|
| Small | 43% | 28 lb |
| Medium | 29% | 41 lb |
| Large | 19% | 64 lb |
| Giant | 14% | 88 lb |
Same puppy, same scale reading, and the answer ranges from a lapdog to a Great Dane. That is why the size category matters more than the weight itself -- get it from the breed or the parents before trusting any number.
Growth curve: share of adult weight by age
How much of the finished dog you are looking at, at each age. Small breeds are essentially done by a year; giants are barely two-thirds there.
| Age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 8 wk | 24% | 17% | 12% | 10% |
| 12 wk | 43% | 29% | 19% | 14% |
| 16 wk | 65% | 45% | 27% | 19% |
| 20 wk | 82% | 62% | 38% | 25% |
| 26 wk | 95% | 82% | 57% | 37% |
| 36 wk | 99% | 96% | 82% | 60% |
| 52 wk (1 yr) | 100% | 100% | 97% | 87% |
| 78 wk (1.5 yr) | 100% | 100% | 100% | 99% |
What to watch instead of the scale
- Body condition, not weight. Ribs easily felt under a thin fat layer, a visible waist from above, a tucked belly from the side. A puppy that fits that is growing right whatever the number says.
- Large and giant puppies grow slower on purpose. Overfeeding them for faster growth raises the risk of hip and elbow dysplasia; large-breed puppy food is lower in calories and calcium for exactly this reason.
- Re-weigh every 2-4 weeks. Two readings a month apart give a growth rate, and the rate is what the estimate is really built on.
Frequently Asked Questions
How accurate is a puppy weight prediction?
Within about 10-15% for a purebred puppy of known adult size measured between 12 and 20 weeks, less for mixed breeds and very young puppies. The biggest source of error is guessing the wrong size category -- a mixed-breed 'medium' that turns out to have a large-breed parent can finish 30-40% heavier than predicted.
Why does the simple 'weight ÷ weeks × 52' rule give a different number?
It assumes a puppy gains the same amount every week for a year. Small breeds finish growing by 9-12 months so the rule overshoots them; giant breeds keep growing to 18-24 months so it undershoots. The size-adjusted estimate uses a growth curve with the right finish line for each size.
At what age is a puppy half its adult weight?
Roughly: small breeds around 3-4 months, medium 4 months, large 5-6 months, giant 6-7 months. That is the 'double it at X weeks' family of rules you see quoted -- they are all this curve read at one point.
Can I use the parents' weights instead?
Yes, and for a purebred it is often better: the average of the sire and dam's adult weights, with males landing toward the upper end and females toward the lower. Use the calculator to sanity-check that against how the puppy is actually growing.
These calculators use published veterinary formulas and are for general guidance. They are not a diagnosis and do not replace your veterinarian, who knows your animal's breed, history, and body condition.