Puppy adult weight predictor
Current age and weight give an estimated adult weight range. The method used is shown every time, because these are rules of thumb and you should be able to see which one you got.
These are estimates, not measurements. Adult size varies with breed, sex, nutrition, whether the dog is neutered and when, and plain genetics. A crossbreed can land anywhere between its parents. Treat the range as a planning number for crate and harness sizes, not a promise.
The methods
| Size class | Method | Source |
|---|---|---|
| Small and toy | Weight at 6 weeks x 4, or weight at 8 weeks x 3. Published wording: "multiply the puppy's weight at 6 weeks old by 4 or their weight at 8 weeks old by 3". | PetMD, reviewed by Sandra C. Mitchell, DVM, DABVP |
| Medium to large | Weight at 4 months, that is 16 weeks, x 2. Published wording: "multiply the puppy's weight at 4 months of age by 2". | PetMD, reviewed by Sandra C. Mitchell, DVM, DABVP |
| All sizes, 6 months and older | The growth percentage method. A puppy is a known percentage of its adult weight at a given age, and that percentage differs by size class. Divide the current weight by that percentage. At 6 months a small breed is about 75 percent grown, a medium 66 percent, a large 60 percent and an extra large 50 percent. | American Kennel Club percentage of adult weight chart |
| Mixed breed of unknown parentage | Vets fall back on paw size, leg length, body build, sex and the size of the parents where known. These are informal indicators used when better information is missing, not a method with a stated accuracy. The AKC adds that if you can still feel the knobs of the ribs, the dog will probably grow taller, and says outright that for a mixed breed puppy of 6 to 10 weeks it is "a bit of a guessing game". | PetMD and American Kennel Club |
When puppies stop growing
| Size class | Adult weight | Finishes growing |
|---|---|---|
| Toy and small | Under about 9 kg, 20 lb | AKC says 6 to 8 months, VCA says 6 to 12 months, PetMD says 8 to 12 months for toy breeds and 9 to 12 months for small. Roughly, done inside the first year. |
| Medium | About 9 to 23 kg, 21 to 50 lb | Around 12 months, PetMD stretches it to 12 to 15 months. |
| Large | About 23 to 45 kg, 51 to 100 lb | AKC and VCA say 12 to 18 months, PetMD says 15 to 18 months. |
| Extra large and giant | Over about 45 kg, 100 lb | 18 to 24 months. Merck says large and giant breeds can take almost two years, and the AKC names mastiffs as growing up to 24 months. |
Common questions
How accurate is a puppy adult weight prediction?
It is a rule of thumb, not a measurement. None of the veterinary sources present these methods as clinically validated. They get noticeably better after 12 weeks, and better again after 6 months, because more of the growth has already happened. For a purebred puppy the published adult range for the breed is a better guide than any formula.
How do I estimate my puppy's adult weight?
For a small breed, multiply the 6 week weight by 4 or the 8 week weight by 3. For a medium to large breed, multiply the 16 week weight by 2. From 6 months on, use the growth percentage method: divide the current weight by the fraction of adult weight typical for that size class at that age.
Why do the two methods give different answers?
Because they disagree. Doubling the 16 week weight assumes a puppy is 50 percent grown at 4 months. The AKC chart puts a large breed at only 60 percent grown at 6 months, which back projects to well under 50 percent at 4 months. For a large breed the doubling rule tends to under predict. Puplr uses the doubling rule below 6 months and the percentage chart above it, and tells you which one it used.
Do paw size and the size of the parents predict adult weight?
Not reliably. Vets use paw size, leg length, build, sex and parent size precisely when the reliable input, a known breed with a known adult range, is missing. They are fallbacks, not a method.
What changes a puppy's adult size?
Breed, sex, build, nutrition in both quality and quantity, and neuter status and timing, because desexing affects when the growth plates close. Overfeeding raises the growth rate in a way that is incompatible with proper skeletal development, so a puppy that grows faster is not a puppy that ends up bigger and healthier.
Next
- Feeding calculator, which asks for the adult size class you just worked out.
- Breed guides with published adult weight ranges.
Sources
- PetMD, when do dogs stop growing, reviewed by Sandra C. Mitchell, DVM, DABVP: https://www.petmd.com/dog/general-health/when-do-dogs-stop-growing
- American Kennel Club, when does my puppy finish growing, percentage of adult weight chart: https://www.akc.org/expert-advice/health/when-does-my-puppy-finish-growing/
- American Kennel Club, breed weight chart: https://www.akc.org/expert-advice/nutrition/breed-weight-chart/
- VCA Animal Hospitals, when will my puppy mature: https://vcahospitals.com/pediatric/puppy/behavior-training/when-will-my-puppy-mature
- MSD Veterinary Manual, routine care of dogs, puppy care: https://www.msdvetmanual.com/dog-owners/routine-care-of-dogs/puppy-care
- MSD Veterinary Manual, feeding practices in small animals: https://www.msdvetmanual.com/management-and-nutrition/nutrition-small-animals/feeding-practices-in-small-animals
Last reviewed 2026-09-05.