Puppy adult weight calculator

Projects adult weight from a puppy's current weight and age — and, on our breed pages, checks that projection against the breed's published adult range.

Projected adult weight

Enter a weight and an age in weeks.

How the projection works

Puppies reach a reasonably predictable share of their adult weight at a given age, and that share depends on eventual adult size rather than on breed as such. Small dogs finish early — many are near adult weight by ten months. Giant breeds are still filling out well past eighteen months. The calculator interpolates the share for the age you enter and divides current weight by it.

The growth shares used here are approximations drawn from conventional guidance rather than from a single published dataset, so the output is given as a range and should be read as one. Anyone presenting a puppy weight prediction as an exact figure is overstating what the method can do.

The check that makes this useful. A projection alone cannot tell you whether it is plausible. On each breed page the same calculator is bounded by that breed's published adult weight range, so a projection that falls outside it is flagged rather than quietly reported — which is the case actually worth knowing about.

What throws it off

Mixed parentage. Adult size in mixes is genuinely hard to predict, and no formula fixes that.
An uncertain birth date, common with rescues. Two weeks of error at twelve weeks old moves the answer a lot.
Being over- or underweight now. The method assumes the puppy is at a healthy condition today; if it is not, the projection inherits the error.
Growth spurts. Weight does not accumulate smoothly, so a single weighing can land on a peak or a trough.

Large and giant breeds have a specific reason to care about growth rate rather than only final size: growing too fast is associated with developmental joint problems. If a projection comes out well above the breed's range, that is a question for a vet rather than a cause for satisfaction.