How big will my puppy get?
Pick your puppy's expected size, the age at a weigh-in and the weight then. The calculator uses the rule its veterinary source gives for that age, and says when there isn't one.
How the estimate works
There's no single formula that fits every puppy, so the calculator uses the rule its source gives for the age you pick:
- Under 6 months, veterinarian Sandra C. Mitchell's rules on PetMD: for small and toy breeds, the weight at 6 weeks times 4, or at 8 weeks times 3; for medium and large breeds, the weight at 4 months times 2.
- From 6 months, the American Kennel Club's growth chart, which shows roughly how much of their adult size puppies have reached at each age. The calculator divides the weight by that share.
An example: a medium puppy weighing 30 lb at 6 months is at about 66% of adult size on AKC's chart, so 30 ÷ 0.66 gives roughly 45 lb as an adult.
Puppy growth chart by percentage
AKC's chart, by adult size. It calls the numbers approximate, and the calculator applies them to weight.
| Age | Small up to 20 lb | Medium 21–50 lb | Large 51–100 lb | Extra-large over 100 lb |
|---|---|---|---|---|
| 6 months | 75% | 66% | 60% | 50% |
| 9 months | 90% | 85% | 75% | 65% |
| 12 months | 100% | 95% | 85% | 80% |
| 15 months | 100% | 100% | 95% | 90% |
| 18 months | 100% | 100% | 100% | 100% |
Source: American Kennel Club, Puppy Growth Chart By Percentage.
When puppies are fully grown
Bigger dogs grow for longer. PetMD's ages, with its own weight groups:
| Size | Adult weight | Usually fully grown at |
|---|---|---|
| Toy | 5–12 lb | 8–12 months |
| Small | 12–24 lb | 9–12 months |
| Medium | 24–59 lb | 12–15 months |
| Large | 59–99 lb | 15–18 months |
| Giant | over 100 lb | 18–24 months |
Source: PetMD. AKC's chief veterinarian gives similar ages: small breeds by 6–8 months, medium around 12 months, giant breeds 12–18 months, and some very large breeds such as Mastiffs up to 24 months.
Puppies grow taller while the growth plates at the ends of their long bones are still open. AKC notes that if you can still feel the "knobs" along the ribs, which are growth plates too, your dog is probably still growing. After height stops, dogs keep filling out with muscle and fat.
Why the estimate can miss
Breed, the parents' size, sex, health and diet all affect adult weight, and a multiplied number isn't a growth curve. Mixed breeds are the hardest: AKC's chief veterinarian calls guessing their final size a guessing game, especially at 6–10 weeks. For a closer picture, weigh your puppy regularly and compare the trend with growth charts with your vet. WALTHAM's puppy growth charts, built from 50,000 healthy dogs, are made for exactly that, from 12 weeks to adulthood.
Grow them lean
AKC's chief veterinarian warns that obesity in puppies can predispose them to joint problems later, such as hip dysplasia, so a fit, leaner puppy is better than a chubby one. Large and giant breeds are also more sensitive to too much or too little calcium while their bones grow. The food calculator turns AAHA's energy guidelines into cups or cans for a growing puppy.
Questions owners ask
How accurate is a puppy weight calculator?
It gives a ballpark, not a promise. The rules come from averages, and breed, parents' size, sex, health and feeding all change the result. AKC's growth percentages are themselves approximate. Weighing your puppy over time and comparing with growth charts with your vet tells you more.
Does a puppy double its weight at 4 months?
PetMD's rule for medium and large breeds is the reverse: the adult weight is about double the weight at 4 months. For small and toy breeds, it uses the weight at 6 weeks times 4 or at 8 weeks times 3.
How big will my mixed-breed puppy get?
It's harder to say. AKC's chief veterinarian calls it a guessing game for dogs of unknown heritage, especially at 6–10 weeks. Use a weigh-in from a later age if you can, and ask your vet which size group fits.
Do paws predict how big a puppy will get?
None of the sources used here give a paw-size rule. Use weight at a known age, and the parents' size if you know it.
When will my puppy stop growing?
AKC says small breeds usually stop growing by 6–8 months and medium breeds at around 12 months, while giant breeds grow until 12–18 months and some, such as Mastiffs, until about 24 months.