“How big will he get?”, every breeder's most-asked question, answered honestly: an adult weight range from age, current weight, and size-class growth curves.
Enter the puppy's age and current weight, pick the expected size class, and we'll estimate the adult weight range plus when they'll finish growing.
At any age, a puppy has reached a knowable fraction of adult weight, but that fraction depends on how big the breed gets. At 16 weeks a toy puppy is ~70% grown while a Great Dane is barely past 40%. And the honest answer always starts with the parents: dam and sire weights beat any formula.
Decent for medium breeds only, it undershoots giant breeds badly and overshoots toys.
A rough medium/large shortcut. Toy breeds are closer to ×2.5 and giants closer to ×5.
The fraction-of-adult-weight approach your vet’s growth charts use, adjusted for maturation speed, always shown as a range.
The most reliable predictor is the parents' adult weights, genetics rule. Growth charts are the second-best tool: a puppy's current weight at a known age tells you roughly what fraction of adult weight they've reached, which is how this calculator works. Quick folk rules like 'double the weight at 16 weeks' only fit medium breeds; small breeds are further along at 16 weeks and giant breeds far behind.
It depends almost entirely on adult size: toy breeds finish around 8–10 months, medium breeds around 12–15 months, and giant breeds keep growing until 18–24 months. Skeletal growth ends first; larger breeds keep filling out with muscle for months afterward.
Honest ones give you a range, not a number, individual growth varies about ±15% around any chart, and mixed or unknown parentage widens it further. This one shows the range, tells you what percentage of adult weight the puppy has typically reached, and reminds you that the parents' sizes beat any formula.
Because growth curves differ dramatically by adult size: at 16 weeks a toy puppy has already reached about 70% of adult weight while a giant-breed puppy is barely past 40%. Using the wrong curve is why generic 'multiply by 2' rules mislead people at both ends of the size spectrum.
The numbers behind this calculator come from veterinary literature and clinical references, not folklore:
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