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Methods and accuracy
Last updated October 6, 2026.
How a prediction works
- Size. Each breed has a typical adult weight (below). The growth curves for the six adult-weight groups are blended by that weight, so a breed near a boundary doesn't jump between groups.
- Adult weight. For a known breed, adult weight is current weight divided by the share of adult weight a typical puppy of that size has reached at that age.
- Range. The range runs from the 90th-centile share to the 10th-centile share, so it should hold about 80% of puppies.
- Mixed breed. With no breed, the calculator finds the adult weight that is consistent with its own growth curve at that age and weight.
Where the growth curves come from
We computed them from the dataset published with Salt C, Morris PJ, German AJ, Wilson D, Lund EM, Cole TJ, Butterwick RF (2017), “Growth standard charts for monitoring bodyweight in dogs of different sizes”, PLOS ONE 12(9): e0182064 (doi:10.1371/journal.pone.0182064). The data are weight records from US Banfield Pet Hospitals, 1994 to 2013 (doi:10.17638/datacat.liverpool.ac.uk/377), licensed CC BY 4.0.
Our processing: purebred dogs only, with visits flagged underweight or overweight left out. Each dog's adult weight is the median of its weigh-ins from age 1 year (adult weight under 33 lb), 1.5 years (33 to 66 lb) or 2 years (over 66 lb), up to age 3. About 1.46 million dogs had both puppy and adult weights. Shares of adult weight were computed for each week of age, smoothed, and forced to rise with age. This is our own analysis of their data, not the paper's published charts.
How accurate is it?
We fitted the curves on half of the dogs and scored predictions on the other half, using 120,000 weigh-ins. Across all ages, known-breed predictions missed adult weight by a median of 10.8%, and 79.3% of dogs ended inside the range. For mixed breeds the figures were 11.5% and 80.4%.
| Puppy age | Known breed: typical miss | Inside range | Mixed breed: typical miss | Inside range |
|---|---|---|---|---|
| 08–11 weeks | 17.8% | 78.6% | 21.0% | 80.5% |
| 12–15 weeks | 14.8% | 79.1% | 16.6% | 80.9% |
| 16–25 weeks | 11.6% | 79.2% | 12.4% | 80.3% |
| 26–38 weeks | 9.0% | 79.9% | 9.2% | 80.4% |
| 39–52 weeks | 6.9% | 79.4% | 7.0% | 79.8% |
Typical miss = median absolute error as a share of the dog's real adult weight.
Breed weights
Breed weights come from each breed's own page at the American Kennel Club, read October 6, 2026. For Cane Corso, Spinone Italiano and Bouvier des Ardennes, which AKC lists without weights, we used the FCI breed standards. For mixes we used the Goldendoodle Association of North America, the American Cockapoo Club, the Australian Labradoodle Association of America, and PetMD, Chewy, Hill's Pet Nutrition and Rover where no association publishes weights. Each breed page links its source.
- Where a source gives only a maximum (“under 28 pounds”), we use 85% of it as the typical weight. Where it gives only a minimum, we use 110%.
- Where a source gives no female weight, only that females are smaller, we use 90% of the male weight.
- These choices only affect which growth curve is used, not the breed range shown.
Limits
- The data are US clinic dogs, mostly neutered. Dogs from other places or lines may differ.
- Adult weight here means weight at about 1 to 3 years. Many dogs add a few percent after their first birthday.
- Puppies who are very thin, very heavy or ill don't follow these curves.
An estimate, not veterinary advice. Found a mistake? Tell us.