Guides → Puppies
How big will my puppy get?
You can get a solid estimate from one weigh-in — if you know the trick. Puppies of different sizes don't just end up different weights, they grow on different schedules, and that schedule is the key.
The method in one line
Adult weight ≈ current weight ÷ the fraction of adult size for that age. The whole game is knowing that fraction, which depends on the puppy's eventual size class. Here's the pattern:
| Age | Small | Medium | Large | Giant |
|---|---|---|---|---|
| 8 weeks | ~32% | ~25% | ~20% | ~15% |
| 12 weeks | ~48% | ~40% | ~33% | ~26% |
| 16 weeks | ~62% | ~53% | ~45% | ~37% |
| 6 months | ~85% | ~78% | ~70% | ~60% |
So a 6 kg puppy at 12 weeks projects very differently depending on breed: about 15 kg if it's a medium breed (6 ÷ 0.40), but around 23 kg if it's a giant breed (6 ÷ 0.26), because giants are barely a quarter grown at that age.
When do puppies stop growing?
Bigger dogs grow for longer — sometimes much longer:
| Size class | Adult weight reached |
|---|---|
| Small (under 10 kg) | 9–12 months |
| Medium (10–25 kg) | ~12 months |
| Large (25–40 kg) | 15–18 months |
| Giant (over 40 kg) | 18–24 months |
A toy breed is essentially done by its first birthday; a Great Dane may still be filling out its chest and frame well into its second year, even after it's reached full height.
How accurate is this, really?
For a purebred puppy weighed between 12 and 16 weeks, expect roughly ±10–15%. For mixed breeds, treat the range as wider — you're partly guessing the size class. The single best predictor remains the parents' adult sizes when you know them; the growth-curve estimate is a valuable cross-check, not a competitor.
Don't rush the growing
One tempting mistake: feeding a large-breed puppy heavily to "help it grow." Overfeeding during growth — and growing too fast — is linked to joint and skeletal problems later, especially in big breeds. Aim for steady growth at a lean body condition rather than maximum size as fast as possible. Our calorie calculator gives an appropriate puppy starting point, and your vet can confirm it for your breed.
Frequently asked questions
How can I tell how big my puppy will get?
Divide current weight by the typical growth fraction for its age and size class. A medium puppy at 12 weeks is ~40% grown, so 6 kg now suggests ~15 kg adult. Most reliable at 12–16 weeks.
When do puppies stop growing?
Small breeds around 9–12 months, medium around 12 months, large at 15–18 months, giant breeds 18–24 months.
What predicts adult size best?
The parents' adult weights, if known. Growth-curve estimates from a weigh-in are a strong second opinion, particularly useful when parentage is unknown.