Puppy weight and size calculator

Puppies don’t grow in a straight line. They gain fastest in the first months, then slow down as they near adult size. Growth studies in dogs fit this S-shaped pattern best with a Gompertz curve, which is the model we use.

1. Size class. If you pick a breed, we take its adult weight from the American Kennel Club’s breed weight chart and place it in one of five size classes used in a 2023 study of dog life expectancy (Montoya et al.): toy under 12 lb, small 12–24 lb, medium 24–57 lb, large 57–99 lb and giant 99 lb or more.
2. Body condition. At a body condition of 5 on the 9-point WSAVA chart, today’s weight is the starting point. Otherwise we first estimate the ideal weight, so extra or missing fat doesn’t get projected into adulthood.
3. Share of adult weight. Each size class has three curves: an early, a typical and a late maturing puppy. Each one says what share of adult weight a puppy has at a given age. Dividing today’s weight by those shares gives the low end, the most likely value and the high end of the range.
4. Mixed breed or not sure. We run all five classes and keep the ones whose result lands inside that class’s own weight band. If more than one fits, you see the combined range and no single most likely value, because guessing would hide the uncertainty.

The toy curve is derived from a study of 65 Toy Poodles (Menchetti et al. 2020) and the large curve from a study of four large breeds (Trangerud et al. 2007). The small, medium and giant curves are estimated from published curves and will be refit when we check more data, so treat those results as estimates.

The thin line on the bar is the common “weight ÷ age in weeks × 52” shortcut. It assumes a puppy gains the same amount every week, which is why it can land far from the curve-based range. Every step, source and open question is on our methodology page.