How our figures work

The age-percentage method

A puppy reaches a predictable fraction of its adult weight at a given age, and that fraction depends on how big the dog will eventually be. So we predict adult weight as:

adult weight ≈ current weight ÷ (fraction of adult weight reached at this age)

The fraction comes from a growth curve chosen by size class (small, medium, large or giant). Small breeds grow fast and finish early; giant breeds grow slowly and keep filling out for up to two years, so they sit on very different curves.

The milestones we anchor to

The curves are anchored to widely-published growth milestones:

Size class	Milestone	Fraction of adult weight	Fully grown
Small (< 20 lb)	6 weeks	~25% (×4)	8–12 months
Medium (20–50 lb)	14 weeks	~40% (×2.5)	12–14 months
Large (50–100 lb)	20 weeks	~50% (×2)	14–18 months
Giant (> 100 lb)	24 weeks	~50% (×2)	18–24 months

Across all sizes, most dogs reach roughly 75% of their adult weight by six months. The reference standard for puppy growth is the WALTHAM Petcare Science Institute growth charts, developed with the Royal Veterinary College; the size-class multipliers above are consistent across veterinary and pet-care sources.

An honest note: the milestone percentages and the “fully grown” ages are sourced. The points between milestones are a smooth interpolation along a plausible growth curve — a sensible model, not independently measured data. We say so here so you can weigh the number accordingly.

Breed ranges

On a breed page, the typical adult weight range comes from the breed’s AKC breed standard. Designer and cross breeds (for example the Goldendoodle) have no kennel-club standard, so we label their range as indicative and ask you to pick the size that matches your puppy rather than inventing a precise figure.

How accurate is it?

For a typical purebred whose size class you know, predictions are usually within about 10–15%. Mixed breeds are wider (around ±15%) because the adult size — and therefore the curve — is less certain. Accuracy improves after 8 weeks of age and tightens as your puppy grows, which is why we always show a range, not just a single number.

Privacy

Every calculation runs in your browser. Your pet’s weight, age and breed are never sent to a server.

Not veterinary advice

PawGauge gives general guidance to help you understand your pet’s growth — it is not a substitute for veterinary care. If your puppy seems over- or under-weight, isn’t growing as expected, or you have any health concern, please talk to your vet.