How accurate is this projection?

Population-level, and more accurate for purebreds than mixed-breeds. For a Labrador at 4 months, the projection is usually within 10% of adult weight. For a mixed breed with unclear adult-size heritage, the range widens — the calculator still gives a useful anchor, just with more room on either side.

Should I be feeding my puppy to hit the projection?

No — that would be backwards. Feed your puppy per veterinary guidance (or the food bag's puppy feeding chart), keep body condition in the ideal range, and the puppy will grow at its natural rate. The calculator projects where the puppy is heading; it doesn't tell you how much to feed.

What if my puppy is larger than expected for its age?

Adjust the size-category upward (e.g., medium → large). Some dogs are bigger than their breed would predict because of heritage, frame, or crossbreeding. The goal is to pick the curve that actually matches the puppy's trajectory, not the one you expected them to follow.

CalculatorPuppy growth

Puppy Growth Calculator

Project your puppy's adult weight and growth curve from current age and weight. Works best once the puppy is past 8 weeks.

Loading calculator…

Formula

How this calculator works

Size-category growth curves from Waltham Centre puppy-weight tables.

How this calculator works

Each size category has a typical puppy-growth curve. We find where on the curve your puppy is today, then project forward to the curve's adult-weight point.

1
curve = walthamGrowthCurve(size)
Waltham Centre puppy-weight tables define typical growth curves for each size category. Toy and small breeds reach adult weight by around 10 months; large and giant breeds take 14–18 months.
Waltham Centre for Pet Nutrition; WSAVA puppy growth guidance.
2
positionOnCurve = currentWeight / currentCurveWeight
We find where on the size-curve this puppy's current weight sits, then project forward along the same curve to adult age.
Observational; derived from Waltham reference curves.
3
adultWeight = curve[adultAgeWeeks] × position
Multiply the curve's adult-age weight by the position ratio. A puppy tracking above-median will project above-median adult weight; a slower-growing puppy will project lower.
Waltham Centre.

Context

When to use this calculator

Use this when you're planning for an adult-weight gear transition (crate, harness, bed), scheduling an orthopedic-friendly activity ramp, or just curious how big your puppy is likely to end up. The projection gets more accurate as the puppy ages; at 4–6 months it is usually within 10% for a purebred.

Pair it with the Food and Calorie calculators to plan portion sizes — those factor life stage and shift automatically as the puppy matures.

FAQ

Frequently asked

How accurate is this projection?
Population-level, and more accurate for purebreds than mixed-breeds. For a Labrador at 4 months, the projection is usually within 10% of adult weight. For a mixed breed with unclear adult-size heritage, the range widens — the calculator still gives a useful anchor, just with more room on either side.
Should I be feeding my puppy to hit the projection?
No — that would be backwards. Feed your puppy per veterinary guidance (or the food bag's puppy feeding chart), keep body condition in the ideal range, and the puppy will grow at its natural rate. The calculator projects where the puppy is heading; it doesn't tell you how much to feed.
What if my puppy is larger than expected for its age?
Adjust the size-category upward (e.g., medium → large). Some dogs are bigger than their breed would predict because of heritage, frame, or crossbreeding. The goal is to pick the curve that actually matches the puppy's trajectory, not the one you expected them to follow.