How big will my dog get? This dog size calculator turns your puppy's age and weight into an adult weight estimate, built from the growth records of more than 8,500 dogs weighed as puppies and again as adults.
Works for puppies from 8 weeks to 18 months. Weigh on a home scale, holding the puppy and subtracting your own weight if needed.
Estimated adult weight
Enter age and weight
Add your puppy's age and current weight to see how big it will get.
Growth curve
Typical rangeExpected weightYour puppyBreed standard
Puppies grow along fairly predictable curves, and the shape of the curve depends on how big the dog will be. Furlyo built this calculator from the open dataset behind Salt et al. (2017), a study of bodyweight records from Banfield Pet Hospitals in the United States. The raw records are openly published. We kept visits where the vet recorded a normal body condition. That left 8,547 purebred dogs weighed both as puppies and again at about two to three years old. For each of them we worked out what share of its own adult weight it had at every month of age, which turns the calculator into a puppy weight calculator backed by real dogs.
The size groups follow the adult weight bands used in the study, plus a giant group over 40 kg (88 lb) that the published charts left out. Adult weight here means the weight at about two years.
Each cell shows the typical share of adult weight at that age. Look up your puppy's group and age, then divide its weight by the percentage to get a quick estimate.
| Size group | Adult weight | Example breeds | 3 mo | 4 mo | 6 mo | 9 mo | 12 mo | 18 mo |
|---|---|---|---|---|---|---|---|---|
| Toy | under 14 lb | Chihuahua, Yorkshire Terrier, Pomeranian | 39% | 51% | 69% | 82% | 88% | 92% |
| Small | 14 to 20 lb | Shih Tzu, Dachshund, Miniature Schnauzer | 39% | 51% | 71% | 85% | 89% | 95% |
| Medium | 20 to 33 lb | Beagle, Pug, Boston Terrier | 34% | 46% | 68% | 83% | 88% | 94% |
| Large | 33 to 66 lb | Australian Shepherd, Siberian Husky, Boxer | 31% | 43% | 65% | 84% | 90% | 96% |
| Very large | 66 to 88 lb | Labrador Retriever, Golden Retriever, German Shepherd Dog | 31% | 43% | 66% | 85% | 91% | 96% |
| Giant | over 88 lb | Rottweiler, Great Dane, Mastiff | 27% | 40% | 63% | 82% | 89% | 95% |
For example, a Large group puppy that weighs 20 lb at 4 months is at about 43% of its adult weight, so it is on track for roughly 46 lb. Not sure which group fits? The dog breeds directory lists the adult weight of every breed.
Smaller dogs start much closer to their adult size. At 3 months a toy puppy already carries about 39% of its adult weight, while a giant puppy carries about 27%. By the first birthday every size group in the data was at 88% to 91% of its two-year weight. After that, dogs kept filling out slowly through their second year, and the giants took longest.
That matters for everyday decisions. Buy a crate for the adult size and block off the extra space with a divider. The dog crate size calculator works out both. Keep exercise gentle while bones are still growing with help from the dog exercise calculator. Once your dog is grown, check its target with the dog ideal weight calculator.
A popular shortcut says a puppy's adult weight is twice its weight at 16 weeks. Our data shows why it only works for small dogs:
| Size group | Share of adult weight at 16 weeks | Doubled | Verdict |
|---|---|---|---|
| Toy | 47% | 94% | Close |
| Small | 47% | 95% | Close |
| Medium | 42% | 85% | About 15% too low |
| Large | 40% | 79% | About 21% too low |
| Very large | 39% | 78% | About 22% too low |
| Giant | 36% | 71% | About 29% too low |
Big dogs are further from their adult weight at 16 weeks, so doubling falls short. For a Labrador or a Rottweiler puppy, use the calculator instead of the shortcut.
Divide your puppy's current weight by the share of adult weight that is typical for its age and size. A puppy in the Large group, for example, carries about 43% of its adult weight at 4 months, so a 20 lb puppy is on track for roughly 46 lb. The calculator above does this for any age from 8 weeks to 18 months.
Most of the growth happens in the first year. In the data behind this calculator, every size group was at 88% to 91% of its two-year weight at 12 months. Dogs then kept filling out slowly through their second year. Giant breeds start from a lower share and take the longest.
Only for small dogs. Doubling the 16-week weight lands at about 94% of adult weight for toy dogs and 95% for small dogs. For giant dogs it lands at only 71%, so it underestimates big breeds by roughly a quarter.
Not reliably. Foot size varies with breed type as much as with body size, so a puppy with big paws is not necessarily headed for a big adult. Age, weight, breed and the size of the parents are much better clues.
For half of the dogs in the data, the adult weight fell inside the range the calculator shows. Estimates are less certain for puppies under 3 months, for mixed breeds and for dogs that were sick or underfed while growing. Weigh again every few weeks and the estimate gets tighter.
Leave the breed on mixed and let the calculator pick a size group from your puppy's age and weight. If you know the parents, the adult dog usually lands somewhere between them. A canine DNA test can also flag the main size genes.
The estimates on this page are general guidance for healthy puppies, not a diagnosis. Illness, diet, neutering and genetics all change how a dog grows. If your puppy is far off the expected curve, gaining or losing weight suddenly, or looks too thin or too round, ask your vet.
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