Puppy Adult Weight Predictor

About this calculator

Predicting a puppy's adult weight uses established growth-curve relationships between a puppy's age and current weight, since different breed sizes reach specific fractions of their adult weight at predictable ages — a common rule of thumb for medium and large breeds is that a puppy reaches roughly half its adult weight around 4 to 5 months old, while a simpler, rougher estimate doubles a puppy's weight at 16 weeks (about 4 months) to approximate its adult size, though this varies notably by breed size category, since giant breeds keep growing much longer than toy breeds.

New puppy owners and breeders use this prediction to plan ahead — for choosing the right size of crate, harness and bed before the puppy outgrows a smaller one, for budgeting food and medication doses that scale with adult weight, and for veterinarians estimating whether a puppy's current growth trajectory looks normal for its breed.

This calculator takes your puppy's age in weeks and its current weight and returns an estimated adult weight based on standard puppy growth-curve relationships.