Method and sources
How the Puppy Weight Calculator Works
The short version: we look up how much of its adult weight a puppy of that size usually has at that age, and divide. Here is exactly how, and where the numbers come from.
The formula
Adult weight ≈ current weight ÷ share of adult weight at this age
1. Pick a growth curve for the size class. Each class has curves that show the typical share of adult weight at every week from 8 weeks to 2 years. “Adult weight” means the weight at about 2 years old.
2. Divide. A small puppy at 16 weeks usually has about 46% of its adult weight, so a 9 lb puppy works out at 9 ÷ 0.46 ≈ 20 lb.
3. Turn it into an honest range. We repeat the sum with every curve we have for that class (males and females, slower and faster growers, and a second independent growth table). The lowest and highest results form the range. We also add a margin for individual puppies that switch growth tracks (doubled for giant dogs, which have no published growth standard); it is about ±8% at 3 months and shrinks to about ±2% near adulthood. For the example: 17.9–22.1 lb, shown as 17–23 lb.
4. Draw the path. The chart scales each curve so it passes through today’s weight, which shows the likely path from now to adulthood.
The range is rounded outward (to 0.5 lb or 0.1 kg for small dogs, whole numbers for bigger dogs) so it never looks more precise than it is.
Size classes
| Class | Adult weight | Salt et al. category | Typical breeds |
|---|---|---|---|
| Toy | under 14 lb under 6.5 kg | I (under 6.5 kg) | Chihuahua, Yorkshire Terrier, Pomeranian, Maltese, Toy Poodle, Miniature Pinscher |
| Small | 14–33 lb 6.5–15 kg | II + III (6.5–15 kg) | Shih Tzu, Dachshund, Bichon Frise, Miniature Schnauzer, Pug, Beagle, Boston Terrier, Cocker Spaniel |
| Medium | 33–66 lb 15–30 kg | IV (15–30 kg) | Australian Shepherd, Siberian Husky, Bulldog, Boxer, pit bull type, Basset Hound |
| Large | 66–88 lb 30–40 kg | V (30–40 kg) | Labrador Retriever, Golden Retriever, German Shepherd Dog |
| Giant | over 88 lb over 40 kg | VI (40 kg+): no chart possible | Great Dane, Mastiff, Rottweiler, Saint Bernard, Newfoundland |
Breed placement in the breed list follows Salt et al. (2017) when the study grouped that breed, otherwise the typical adult weight in the AKC breed standard. Some breeds sit on a border (Boxers, for example, were grouped with 15–30 kg dogs). If your puppy’s expected adult weight is clearly in another class, pick that class.
Where the curves come from
Toy to large: Salt et al. 2017. The most detailed growth standards for dogs so far, built from more than 6 million vet-clinic visits by healthy young dogs in ideal body condition (Banfield Pet Hospitals, USA). The study made centile charts from 12 weeks to 2 years for five size categories up to 40 kg. We read the 25th, 50th and 75th centile curves for males and females from the published charts (Figures 7–11) and divide each by its own value at 100 weeks. Between 8 and 12 weeks we extend the curves back with the early growth rate from the NRC table below.
Second opinion: NRC 2006. The National Research Council’s growth table (as printed in the WALTHAM Pocket Book of Puppy Nutrition and Care) gives the share of adult weight by month for dogs under 25 kg, 25–45 kg and over 45 kg. It is part of every range, which widens the range where the two sources disagree.
Giant dogs: NRC 2006 + Hawthorne et al. 2004. Salt et al. could not build a reliable chart for dogs over 40 kg because giant breeds such as Great Danes, Mastiffs and Rottweilers grow too differently. For giants we average the NRC giant table (80% at 12 months) with a curve based on Hawthorne et al., who found giant breeds reach about half their adult weight at about 5 months and 99% at 11–15 months. Giant estimates are therefore rougher.
When growth finishes. The ages shown (toy and small 9–12 months, medium 12–15, large 15–18, giant 18–24) follow common vet guidance from the American Kennel Club and PetMD, and match Hawthorne et al. (toy to medium breeds reach adult weight at 9–10 months, giants at 11–15 months or later).
Rules of thumb vs. growth data
| Rule | Checked for | Curves say | Verdict |
|---|---|---|---|
| Weight at 6 weeks × 4 (toy and small) PetMD and others | Toy | curves start at 8 weeks | can’t check (too young) |
| Weight at 8 weeks × 3 (toy and small) PetMD, Rover | Small | × 4.8 (× 4.3–5.6) | guesses low |
| Weight at 14 weeks × 2.5 (medium) common vet-clinic advice | Medium | × 2.8 (× 2.5–3.1) | about right |
| Weight at 16 weeks × 2 (small) widely quoted | Small | × 2.2 (× 2.0–2.5) | about right |
| Weight at 16 weeks × 2 (medium and large) Rover and others | Large | × 2.4 (× 2.2–2.6) | guesses low |
| Weight at 4 months × 2 (medium and large) PetMD | Medium | × 2.2 (× 1.9–2.3) | about right |
| Weight at 5 months × 2 (giant) common vet-clinic advice | Giant | × 2.0 (× 1.8–2.3) | about right |
| Weight at 6 months × 2 (medium and large) widely quoted | Large | × 1.4 (× 1.4–1.5) | guesses high |
Rules of thumb are handy because they need no table, but each one only fits one size at one age. “Double the weight at 16 weeks” works for small dogs. “Double the weight at 6 months” overshoots for most dogs, because by 6 months most puppies already have 60–70% of their adult weight.
Limits: please read
- Mixed breeds can grow like either parent. Choose the size you expect and treat the range as rough.
- The size class matters most. The same 10 lb at 12 weeks means a very different adult in the small class than in the large class.
- Very young puppies (8–12 weeks) give wide ranges. Weigh again every few weeks; the estimate narrows quickly.
- Weight is not health. A heavy puppy may be overweight rather than big-boned. Ask your vet to check body condition, for example with the WSAVA body condition score chart.
- Neutering shifted growth only slightly in Salt et al.’s data, so the calculator ignores it.
- Reading the charts by eye. The Salt curves were digitised from the published figures (accuracy about ±1%), not taken from the raw data.
Sources
- Salt C, Morris PJ, German AJ, Wilson D, Lund EM, Cole TJ, Butterwick RF. Growth standard charts for monitoring bodyweight in dogs of different sizes. PLoS ONE 2017;12(9):e0182064. Supporting data: University of Liverpool DataCat.
- Hawthorne AJ, Booles D, Nugent PA, Gettinby G, Wilkinson J. Body-weight changes during growth in puppies of different breeds. Journal of Nutrition 2004;134(8 Suppl):2027S–2030S.
- National Research Council. Nutrient Requirements of Dogs and Cats. National Academies Press, 2006. Growth table as reprinted in the WALTHAM Pocket Book of Puppy Nutrition and Care (2012).
- American Kennel Club. When do dogs stop growing?
- PetMD. When do dogs stop growing? (source of the 6-week, 8-week and 4-month rules above).
- WSAVA. Global Nutrition Guidelines and body condition score charts.