Puppy Weight Calculator
Enter the age of your puppy in weeks and its current weight. The calculator gives a rough estimate of its adult weight, in pounds and kilograms.
How to use this Puppy Weight Calculator
- Enter the age of your puppy in weeks.
- Enter the current weight in pounds from a recent weigh-in.
- Keep the age at full size at 52 weeks, or change it for a slow-growing large breed.
- Press Calculate to see the estimated adult weight.
- Weigh again every few weeks and compare the estimates.
How to estimate adult dog weight
The rule of thumb assumes weight rises evenly with age up to full size.
- Adult weight = current weight / age in weeks x age at full size in weeks
- Weight in kg = pounds / 2.2046
- Share now = current weight / adult weight x 100
Worked example
A puppy is 16 weeks old and weighs 20 lb. The estimate is 20 / 16 x 52 = 65.0 lb, or 29.5 kg. That means the puppy has about 45 lb still to gain, and is at about 31% of its adult weight today.
This simple rule is only a guide. Puppies do not gain weight at a steady rate. Most grow fast early on and then slow down, so a straight-line estimate often overshoots for young puppies and undershoots for others. Mixed breeds are the hardest to predict. Compare the result with the breed standard if your puppy is a purebred, and weigh it every two weeks to see the trend. A vet can give a better estimate from the size of the paws, the frame and the parents, and can tell you if the puppy is growing too fast or too slowly.
Assumptions & limits
- The estimate assumes steady growth, which is not how puppies grow. Real growth is fast at first and then slows.
- The age at full size is an input. Large and giant breeds may keep growing past one year.
- Breed, parents and diet all change the result. It is not suited to mixed breeds with unknown parents.
- The result is an estimate and not a diagnosis. A puppy that is much heavier or lighter than expected should see a vet.
- It does not account for a healthy body condition. Check with a vet.
Frequently asked questions
How do I estimate my puppy adult weight?
Divide the current weight by the age in weeks and multiply by the age at full size in weeks. At 16 weeks and 20 lb the estimate is 65 lb.
How accurate is it?
It is only a rough guide. Growth is not steady and breed matters a lot.
When do puppies stop growing?
Small breeds may finish by about a year. Large breeds can keep growing for longer.
Does it work for mixed breeds?
It can give a guide, but it is less reliable when the parents are unknown.
How often should I weigh my puppy?
Every one to two weeks, so you can see the trend.
Should I ask a vet?
Yes, especially if the puppy seems to be growing very fast or very slowly.
Related calculators
Related articles
Last updated: November 2026