OneTaskBy Tim King · Updated
Puppy Weight Calculator
Likely Adult Weight Range From Age in Weeks, Current Weight and Expected Size
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How the Puppy Weight Calculator works
This puppy weight calculator estimates how heavy your puppy will be when fully grown. Enter its current weight, its age in weeks and the size class you expect, and it shows the predicted adult weight, a likely range and how far through its growth the puppy already is.
How the puppy weight calculator works
Puppies grow fast at first and then slow down, and bigger breeds keep growing for longer. Small dogs are usually close to adult weight by 10 to 12 months, while giant breeds can keep filling out until 18 to 24 months. The calculator uses a rule-of-thumb growth curve for each size class that gives the share of adult weight a typical puppy has reached at each age. The formula is adult weight = current weight ÷ share reached.
First example. A 12-week-old puppy weighing 6 kg that should be a medium dog has reached about 30% of its adult weight. The estimate is 19.7 kg (43.5 lb), with a likely range of 16.8 to 22.7 kg.
Second example. A 16-week-old large-breed puppy weighing 10 kg is about 35% grown, so the estimate is 28.4 kg (62.5 lb). Growth usually finishes at around 18 months for a dog of this size.
How many weeks until a puppy reaches half its adult weight? About 13 weeks for small breeds, 18 to 19 weeks for medium dogs, 23 weeks for large dogs and 28 weeks for giant breeds.
The calculator also shows the popular weeks rule (weight ÷ age in weeks × 52) for comparison. It tends to overestimate small breeds and is only a rough guide. Mixed breeds and puppies that were unusually small or large at birth can land outside the range.
Share of adult weight reached by age, by adult size (rule-of-thumb growth curves)
| Age (weeks) | Age (months) | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 8 | 1.8 | 25% | 20% | 16% | 12% |
| 10 | 2.3 | 31% | 25% | 20% | 16% |
| 12 | 2.8 | 37% | 30% | 25% | 19% |
| 14 | 3.2 | 44% | 36% | 30% | 23% |
| 16 | 3.7 | 51% | 42% | 35% | 28% |
| 18 | 4.1 | 58% | 47% | 40% | 32% |
| 20 | 4.6 | 63% | 52% | 44% | 35% |
| 22 | 5.1 | 68% | 57% | 48% | 39% |
| 24 | 5.5 | 73% | 62% | 53% | 43% |
| 26 | 6.0 | 78% | 66% | 57% | 47% |
| 28 | 6.4 | 81% | 69% | 60% | 50% |
| 30 | 6.9 | 83% | 72% | 64% | 53% |
| 32 | 7.4 | 86% | 75% | 67% | 56% |
| 34 | 7.8 | 89% | 78% | 70% | 59% |
| 36 | 8.3 | 91% | 81% | 73% | 63% |
| 38 | 8.7 | 93% | 84% | 76% | 66% |
| 40 | 9.2 | 94% | 86% | 79% | 69% |
| 42 | 9.7 | 96% | 89% | 82% | 72% |
| 44 | 10.1 | 97% | 91% | 84% | 74% |
| 46 | 10.6 | 98% | 92% | 86% | 76% |
| 48 | 11.0 | 99% | 93% | 87% | 78% |
| 50 | 11.5 | 99% | 95% | 89% | 80% |
| 52 | 12.0 | 100% | 96% | 91% | 82% |
FAQ
How can I tell how big my puppy will get?
Use its current weight and age with the expected adult size, as this calculator does. The parents' weights are also a good guide, and large paws or loose skin can hint at more growth still to come.
At what age is a puppy half its adult weight?
Small breeds are usually half grown at around 3 months, medium dogs at around 4 to 5 months, large dogs at about 5 months and giant breeds at 6 months or later, because they keep growing for longer.
Is the weeks rule accurate?
Weight ÷ age in weeks × 52 is easy to remember, but it assumes steady growth all year. It works best for medium dogs and tends to overestimate small breeds, which finish growing earlier than a year.
When do dogs stop growing?
Small dogs usually stop at around 10 to 12 months, medium dogs at about 12 to 15 months, large dogs at 15 to 18 months and giant breeds such as Great Danes at 18 to 24 months.
Why does my puppy's estimate change from week to week?
Puppies grow in spurts and their weight swings with meals, play and growth stages. Weigh at the same time of day every week or two and expect the estimate to settle as the puppy gets older.
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