Every PupGauge result is a range, and every range comes from a published source, a number we derived from that source, or a plainly-labelled PupGauge choice. This page separates the three, so you can see exactly where a number comes from before you trust it.
Puppy weight and adult size
Sourced. The growth curve comes from Hawthorne et al. (2004), a study of 173 puppies across 12 breeds, weighed every week from birth (or from 8–11 weeks old) until about 12 months (toy to medium breeds) or 18 months (large and giant breeds). The paper fits each breed to a logistic growth curve: weight at a given age depends on the breed’s adult weight, an age where the puppy reaches half its adult weight, and a growth-rate value. Toy, small and medium breeds reached 99% of adult weight around 9–10 months in this data; large and giant breeds around 11–15 months.
Derived. Hawthorne’s paper only fits 12 specific breeds. To estimate a curve for any adult weight, we fit a regression of the two curve parameters against the natural log of adult weight, across those same 12 breeds, and use that regression for every calculation. We checked the regression against each of the 12 published curves: it lands within about 10% of the true breed curve by 4 months, and within 1–3% by a year, with the widest errors (up to ~25%) in the first 8 weeks, where any puppy’s trajectory is naturally hardest to predict.
Estimate. From your puppy’s age and weight today, the calculator solves for the adult weight that makes the curve fit. If you gave a breed or size group, that adds a second, independent estimate (the breed’s standard adult weight), and the two are blended — weighted toward the growth curve as your puppy gets closer to full size, and toward the breed standard while they’re young, since a single weigh-in early on is the least reliable signal.
Range, not a point. The uncertainty band widens the less grown your puppy is, is wider again without a breed or size group, and wider still for giant breeds, whose growth is the least uniform in the source data. It’s built to be at least as wide as the regression’s own error at that stage of growth, before adding room for how much individual puppies vary — which is why very young puppies get a wide range, and puppies close to adult size get a narrow one.
When we don’t show a number. Under 8 weeks, growth is too unpredictable for any curve, so there’s no estimate. At or past the age your puppy’s breed or size group is normally fully grown, we say so instead of guessing further. If the age and weight you entered imply an adult size wildly outside the breed you picked — more than double the top of its standard range, or under half the bottom — we flag a likely breed or unit mismatch rather than blend in a number that’s probably wrong.
Size groups
When you don’t know a breed, PupGauge sorts puppies into five weight-based size groups, informed by the category cut-offs in Salt et al. (2017):
| Group | Adult weight | Usually full size |
|---|---|---|
| Toy | up to 6.5 kg (14 lb) | 9–12 months |
| Small | 6.5–15 kg (14–33 lb) | 9–12 months |
| Medium | 15–25 kg (33–55 lb) | 9–12 months |
| Large | 25–40 kg (55–88 lb) | 11–15 months |
| Giant | 40–80 kg (88–176 lb) | 15–24 months |
“Usually full size.” For toy to large dogs, these windows are based on the ages at which Hawthorne’s breeds reached 99% of adult weight (about 9–10 months for toy to medium breeds, 11–15 months for large and giant breeds), rounded out a little. For giant dogs, 15–24 months is a PupGauge choice. It is later than the growth curve, which reaches 99% of adult weight at about 12 months for a 60 kg dog, because giant breeds keep maturing after their weight levels off: the AKC says giant-breed puppies grow until 12–18 months, and very large breeds like Mastiffs may not be fully grown until 24 months.
Breed data. When you pick a breed, its adult weight range is copied from the AKC’s own published breed standard for that breed, separated by sex where the standard gives one. Breed standards describe an ideal, not a measured average — a real dog can fall outside it and still be healthy.
Dog age in human years
Sourced. Life-stage boundaries (puppy, young adult, mature adult, senior) follow the AAHA’s 2019 Canine Life Stage Guidelines. The early human-year equivalents (about 15 human years in the first year, roughly 9 more in the second) follow AVMA guidance. That larger dogs age faster after the first two years is established in Kraus et al. (2013). Median lifespan by size — used to decide when “senior” starts — comes from McMillan et al. (2024): about 12.7 years for small dogs, 12.5 for medium, 11.9 for large. The separate DNA-methylation comparison line shown on the age result (human age ≈ 16·ln(dog age) + 31) is from Wang et al. (2020), a study specifically of Labrador Retrievers — it’s shown as a labelled comparison, not the main estimate, because it hasn’t been validated across breeds and sizes the way the AAHA/AVMA figures have.
PupGauge choices. After age two, we add human years per dog year by size — 4 for toy and small, 5 for medium, 6 for large, 7 for giant — which is a smoothed reading of the AVMA/Kraus pattern, not a single published table. Giant breeds’ median lifespan isn’t in the McMillan data, so we use 10 years for them, our own estimate based on the pattern for large breeds. If you don’t give a size, we default to medium and show how a small and a large dog would compare at the same age.
We don’t use the old “multiply by 7” rule anywhere in this calculator — it was never based on a real study, and both the growth pattern and the lifespan data above show why it’s a poor fit for either end of the size range.
Feeding, weight, water, breeding and crate calculators
Eight further calculators (October 2026) follow the same rules: a published method, ranges where the evidence supports them, and a plain statement of limits. Each tool page shows its formula and sources in full.
| Calculator | Method | Main sources |
|---|---|---|
| Dog calorie calculator | RER = 70 × kg0.75 × life-stage factor (Merck point, AAHA range); 10% treat allowance; amount = kcal ÷ label kcal | Merck Veterinary Manual; 2021 AAHA Nutrition Guidelines; Bermingham 2014 meta-analysis |
| Ideal weight calculator | Ideal = weight ÷ (1 + 0.1 × (BCS − 5)); loss calories 1.0 × RER at target (0.8 shown as vet option); pace 1–2% per week | 2014 AAHA Weight Management Guidelines; 2021 AAHA Guidelines |
| Puppy feeding calculator | Start: (1.063 − 0.565p) × kg0.75 MJ; upper guide: NRC growth equation; p = current ÷ adult weight | Klein et al. 2019 (493 owned puppies); NRC 2006 |
| Water intake calculator | Normal 44–66 mL/kg/day minus water in wet food; excessive thirst > 100 mL/kg/day | Merck Veterinary Manual; Schoeman, WSAVA 2008 |
| Food cost calculator | Exact arithmetic from label kcal, pack size and price at the dog’s daily calories | AAFCO PF9 calorie statements; Tufts Petfoodology |
| Crate size calculator | Home: length/height + 2–4 in; air: A + ½B × 2C × D (+10% snub-nosed) | IATA Live Animals Regulations (2026); PetSmart sizing guide; AKC |
| Heat cycle calculator | Own average interval (window = shortest/longest gap ± 2 weeks, labelled allowance) or population 7 months (4½–10) | UC Davis (Gardiner 2019); Threlfall (DVM360) |
| Pregnancy calculator | Whelping 58–72 d after first mating, 64–66 d after LH surge, 62–64 after ovulation, 56–58 after diestrus day 1 | Merck Veterinary Manual (2025); Concannon 2000; AKC |
Rejected on purpose: a “dog BMI” (no validated canine BMI exists), raw-feeding percentage-of-body-weight calculators (folk rules without validation) and medication or toxicity dose calculators (clinical decisions that need a vet).
What this isn’t
PupGauge gives estimates from population-level data, not a diagnosis or a promise about your individual dog. A puppy who’s consistently outside the range we show, gaining weight unusually fast or slowly, or showing any sign of ill health, is worth a vet visit regardless of what a calculator says. Nothing on this site replaces that.
Sources
- 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.
- Salt C, Morris PJ, German AJ, et al. Growth standard charts for monitoring bodyweight in dogs of different sizes. PLOS ONE. 2017;12(9):e0182064.
- American Animal Hospital Association. 2019 AAHA Canine Life Stage Guidelines.
- American Veterinary Medical Association. How to calculate your dog’s age (life-stage guidance).
- Kraus C, Pavard S, Promislow DEL. The size-life span trade-off decomposed: why large dogs die young. The American Naturalist. 2013;181(4).
- McMillan KM, Bielby J, Williams CL, et al. Longevity of companion dog breeds. Scientific Reports. 2024;14:531.
- Wang T, Ma J, Hogan AN, et al. Quantitative translation of dog-to-human aging by conserved remodeling of the DNA methylome. Cell Systems. 2020;11(2).
- American Kennel Club. Official breed standards (adult weight, by breed).