Enter your puppy's breed, current age, and weight. The calculator projects adult weight using breed-specific growth curves derived from published WALTHAM and Hill's puppy-growth research. Works for 100+ purebreds and common mixes; falls back to a size-group estimator for everything else.
Track this over time, not just once. A single projection has ±15% uncertainty for purebreds, more for mixes. The trajectory across multiple weigh-ins is what actually predicts adult size. Open DenLumen to log every weigh-in and see the curve converge.
Puppy growth follows a sigmoid curve that flattens as the dog approaches adulthood. The percentage of adult weight reached at any given age is well-documented in veterinary nutrition research. We use the size-group-aware version of that table:
| Age | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 8 weeks | 22% | 17% | 14% | 11% | 8% |
| 12 weeks | 30% | 26% | 22% | 19% | 14% |
| 16 weeks | 43% | 38% | 34% | 29% | 22% |
| 20 weeks | 54% | 50% | 44% | 38% | 30% |
| 26 weeks (6 mo) | 71% | 66% | 60% | 52% | 43% |
| 39 weeks (9 mo) | 92% | 88% | 80% | 71% | 59% |
| 52 weeks (12 mo) | 100% | 96% | 90% | 82% | 72% |
| 78 weeks (18 mo) | — | 100% | 100% | 95% | 87% |
| 104 weeks (24 mo) | — | — | — | 100% | 100% |
The math: given current age and current weight, divide weight by the appropriate percentage to project adult weight. We then constrain the result to the breed-typical range (AKC standard low and high) so a high-energy puppy on a steep trajectory doesn't project to twice its breed's standard size — the constraint reflects the biological reality that adult size is bounded by genetics, not just current trajectory.
A toy breed has finished 22% of its growing by 8 weeks; a giant breed has finished only 8%. If you ignore the group and use a single coefficient, you'll over-project toy breeds and under-project giants by 50%+ in either direction. The calculator handles this by mapping breed → size group → group-specific coefficient.
The calculator's catalog includes 100+ breeds with their AKC standard adult weight ranges and full-growth ages. Highlights — all the high-search-volume mixes are in:
Don't see your breed in the autocomplete? Pick the closest size-group match and the calculator uses the group-average curve. Accuracy degrades from ±15% to ±25% on size-group-only projections.
Breed-specific calculators are accurate to within roughly ±15% of adult weight when you input a known purebred and current age and weight are recent. Mixed-breed projections are less precise — ±25% is realistic. The trajectory matters more than any single projection: re-check every 2–4 weeks and the curve gets more accurate.
Toy and small breeds finish growing by 9–12 months. Medium breeds by 12–15 months. Large breeds by 15–18 months. Giant breeds (Great Dane, Mastiff, Saint Bernard) keep growing until 24 months. Weight gain often continues 1–2 months past skeletal maturity as muscle fills out.
If you know the parent breeds, take the average of their typical adult weights. If you don't, look at your puppy's paws — disproportionately large paws relative to body size usually predict a larger adult. Or use the size-group estimator: pick small, medium, large, or giant based on what you observe at the vet, and the calculator uses group-average coefficients.
Breed standards are AKC show ranges, not absolute limits. Most pet-bred puppies (non-show-line) run 10–20% above standard. If your puppy is tracking 30%+ above standard at multiple weigh-ins, mention it at the next vet visit — sustained over-growth in large breeds can stress developing joints.
One projection has ±15% uncertainty. A series of projections converges fast — DenLumen logs every weigh-in and charts the curve, with comparison to your breed standard.
Open DenLumenStep-by-step instructions for the features on this page: