What this calculator does
A dog weight chart usually means a table of average adult weights by breed, but breeds vary so much in adult size that a single chart cannot cover them all. This calculator instead uses one specific, commonly cited veterinary rule of thumb: for a medium or large breed puppy, weigh it at around 14 to 16 weeks old and double that figure for a rough estimate of its adult weight.
This is a dog weight calculator built around approximation, not precision. It works reasonably well for many medium and large breed dogs weighed close to the 14-16 week mark, and gets steadily less reliable the further the puppy is from that age, or for toy and small breeds, which mature on a different curve entirely.
The formula
Enter the puppy's current weight and current age in weeks. The estimate is simply that weight doubled. The calculator also flags whether the current age falls inside the 14-16 week window the rule of thumb is based on, because the further outside that window the reading is taken, the less the doubled figure means.
| Term | Meaning |
|---|---|
| Weight at 14-16 weeks | The age range this particular rule of thumb was built around; it is not accurate at other ages. |
| Adult weight estimate | The puppy's current weight doubled, a rough approximation rather than a breed-specific prediction. |
| Reliability window | A flag showing whether the current age is close enough to 14-16 weeks for the estimate to be reasonably meaningful. |
The inputs explained
| Field | What to enter |
|---|---|
| Puppy's weight now (kg) | The puppy's weight as measured today, on a kitchen or vet scale. |
| Puppy's age now (weeks) | The puppy's age today, in weeks, not months. |
When to use it
A new medium or large breed puppy
Weighing a puppy at its 14-16 week vet visit and doubling that figure gives a rough sense of the adult size to expect, useful for planning crate size, food budget or whether a rental or lease has a weight limit.
A puppy weighed outside the 14-16 week window
The same doubling arithmetic still runs, but the calculator flags that the estimate is unreliable outside that window, since growth rate is not constant across a puppy's first year.
Toy and small breeds, or giant breeds
This rule of thumb is specifically for medium and large breeds; toy and small breeds reach adult weight much earlier and giant breeds keep growing well past six months, so this calculator is not a good fit for either, an important limit to be upfront about rather than paper over.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
What might a puppy weighed at 15 weeks grow into?
A range of puppy weights taken at 15 weeks, right in the middle of the reliable window, doubled to estimate adult weight.
| Weight at 15 weeks | Estimated adult weight | In pounds |
|---|---|---|
| 3 kg | 6.0 kg | 13.2 lb |
| 5 kg | 10.0 kg | 22.0 lb |
| 7 kg | 14.0 kg | 30.9 lb |
| 9 kg | 18.0 kg | 39.7 lb |
| 12 kg | 24.0 kg | 52.9 lb |
| 15 kg | 30.0 kg | 66.1 lb |
| 20 kg | 40.0 kg | 88.2 lb |
How does the age at weighing affect reliability?
The same 9 kg puppy weight, taken at different ages, showing how the reliability flag changes even though the arithmetic does not.
| Age at weighing | Estimated adult weight | Reliability of this estimate |
|---|---|---|
| 8 weeks | 18.0 kg | Outside the 14-16 week window: this estimate will be less reliable the further the current age is from that range. |
| 11 weeks | 18.0 kg | Outside the 14-16 week window: this estimate will be less reliable the further the current age is from that range. |
| 13 weeks | 18.0 kg | Within the 14-16 week window this rule of thumb is based on. |
| 15 weeks | 18.0 kg | Within the 14-16 week window this rule of thumb is based on. |
| 17 weeks | 18.0 kg | Within the 14-16 week window this rule of thumb is based on. |
| 20 weeks | 18.0 kg | Outside the 14-16 week window: this estimate will be less reliable the further the current age is from that range. |
| 24 weeks | 18.0 kg | Outside the 14-16 week window: this estimate will be less reliable the further the current age is from that range. |
Questions
Is this the same as a breed-specific dog weight chart?
No. A breed-specific chart uses growth data collected for that particular breed, which this calculator does not have. This tool uses one general, breed-independent rule of thumb instead, so treat the result as a rough guide, not a substitute for breed growth data from a vet or breeder.
Why 14 to 16 weeks specifically?
That window is where the doubling rule of thumb has been found to hold up reasonably well for many medium and large breed puppies. Weigh too early and growth has barely started to show adult proportions; weigh too late and the puppy has already grown past the point where doubling still makes sense.
Does this work for small or toy breed puppies?
Not reliably. Small and toy breeds reach most of their adult weight much earlier than medium and large breeds, so doubling a 14-16 week weight tends to overestimate their adult size significantly. This calculator is scoped to medium and large breeds only.
My puppy is a giant breed, is this accurate?
Treat it as a floor rather than a final figure. Giant breeds such as mastiffs or great danes keep growing well past six months of age, so a simple doubling at 14-16 weeks tends to underestimate their eventual adult weight. A vet familiar with the breed is the better source for those dogs.
For everyday feeding amounts once you have a weight to work from, see the dog daily food amount calculator. To convert a dog's age into a human-equivalent age, see the dog age calculator.