What this page sets up
The calculator opens without a breed and with two extra boxes: the mother’s and the father’s adult weight. The example is a 30 lb mother and a 50 lb father, which average 40 lb and put the puppy on the medium-breed curve (25 to 50 lb as adults). A 12 lb puppy at 12 weeks then points to about 40 lb, with 30 to 57 lb as the likely spread, and the line under the result says whether that falls inside the parents’ 30 to 50 lb.
Change either parent and the size class follows their average: make the father 90 lb and the average becomes 60 lb, the large-breed curve, and the same 12 lb puppy points to about 45 lb, because large pups have a smaller share of their adult weight at 12 weeks. Switch to kg and the parents’ boxes switch with the weight.
Where the parents’ weights come from
Ask the breeder or the shelter for both parents’ adult weights. If you only met the mother, use her weight and leave the father’s box empty. Adoption listings often give the puppy’s size as small, medium or large; these are guesses, so let the weigh-ins decide.
How to read the result for a crossbreed
- Inside the parents’ range is the usual case.
- Above both parents happens, especially when one side of the family is bigger than the parent you know. Check the unit and the age first; an age off by two weeks moves the estimate a lot in young puppies.
- Below both parents at an early weigh-in often evens out. Weigh again in three or four weeks; with the Track several option the tool combines the weigh-ins and the range narrows.
A mixed-breed puppy’s body condition matters more than the number: you should be able to feel the ribs without pressing, and see a waist from above. Your vet can judge both at the puppy’s checkups. To see how a dog’s age compares with a human’s once it’s grown, use the dog age calculator.
One limit to keep in mind: the growth curves come from the vet records of purebred dogs in five size classes (Salt et al., 2017, PLOS ONE), because a breed is what tells you a dog’s size class. Using them for a crossbreed assumes it grows like purebreds of the same adult size, which is a reasonable starting point but not something that data measured. The chart below follows a puppy heading for the parents’ 40 lb average.
Mixed breed puppy weight chart
| Age | Mixed breedadult ≈ 40 lb | Share of adult weight |
|---|---|---|
| 8 weeks | 7.4 lb · 3.4 kg | 19% |
| 10 weeks | 9.6 lb · 4.3 kg | 24% |
| 12 weeks | 12.1 lb · 5.5 kg | 30% |
| 16 weeks | 17.3 lb · 7.8 kg | 43% |
| 5 months | 24 lb · 10.7 kg | 59% |
| 6 months | 27 lb · 12.3 kg | 68% |
| 7 months | 30 lb · 13.6 kg | 75% |
| 8 months | 32 lb · 14.5 kg | 80% |
| 9 months | 33 lb · 15 kg | 83% |
| 10 months | 34 lb · 15.5 kg | 85% |
| 1 year | 35 lb · 16 kg | 88% |
| 15 months | 36 lb · 16.6 kg | 91% |
| 18 months | 37 lb · 17 kg | 94% |
| 2 years | 39 lb · 17.7 kg | 97% |
| Adult (2–3 years) | 40 lb · 18.1 kg | 100% |