Our puppy weight calculator takes your puppy’s age and current weight and estimates their adult weight, how much growing is left, and what they should weigh each month until they’re full grown. Pick a breed size if you know it. If you don’t, the calculator will work it out.
How to use the puppy weight calculator
- Enter your puppy’s age in weeks or months. Estimates start to be useful at about 8 weeks old. Before that, puppies grow at very different speeds.
- Enter today’s weight. Weigh yourself holding the puppy, then without, and subtract. A kitchen or baby scale is more accurate for small puppies.
- Choose the expected adult size. Know the breed? Pick its size class. For a mix, or if you’re not sure, choose “Not sure” and the calculator finds the growth curve that best fits your numbers.
You’ll get an estimated adult weight with a likely range, a growth chart, and a month-by-month table for checking that your puppy is on track.
Puppy growth chart: % of adult weight by age
Small breeds grow fast and finish early. Giant breeds take much longer. The chart shows roughly what share of their adult weight puppies of each size have reached at each age.
| Age | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 2 months | 27% | 23% | 22% | 21% | 16% |
| 3 months | 40% | 36% | 33% | 32% | 26% |
| 4 months | 52% | 49% | 45% | 43% | 36% |
| 5 months | 63% | 61% | 57% | 54% | 47% |
| 6 months | 73% | 72% | 68% | 64% | 57% |
| 8 months | 88% | 87% | 84% | 79% | 72% |
| 10 months | 97% | 96% | 94% | 89% | 82% |
| 12 months | 100% | 99% | 98% | 95% | 89% |
| 15 months | 100% | 100% | 100% | 99% | 95% |
| 18 months | 100% | 100% | 100% | 100% | 98% |
Size classes by adult weight: Toy under 10 lb, Small 10–25 lb, Medium 25–55 lb, Large 55–100 lb, Giant over 100 lb.
Worked example
Say you have a 12-week-old Labrador puppy who weighs 22 lb. Labs are a large breed, and large-breed puppies are about 29% of their adult weight at 12 weeks. So 22 ÷ 0.29 ≈ 76 lb. The calculator gives a likely range of about 65–87 lb. That lines up with what most adult Labs weigh.
Quick rules of thumb (and why we don’t rely on them)
You’ve probably seen shortcuts like “double the weight at 4 months” or “double the weight at 6 months for large breeds”. They work for some dogs. The problem is that breeds grow at different speeds. Double a toy puppy’s 4-month weight and you overshoot; double a Great Dane’s and you badly undershoot. We use a separate growth curve for each size class instead, so the estimate stays sensible anywhere from 8 weeks to 18 months.
What decides how big a puppy gets?
- Genetics matter most. The parents’ size is the best predictor for any puppy. For mixed breeds, try our dog size calculator, which can include the parents’ weights.
- Males of most breeds end up 5–15% heavier than females.
- Nutrition counts too. Underfeeding can stunt growth, and overfeeding makes puppies heavy, not taller. Extra weight while growing is hard on young joints, especially in large and giant breeds.
- The timing of spaying or neutering can slightly change growth plate closure and body composition. Ask your vet what timing suits your breed.
- Big paws can hint at a bigger dog, but on their own they’re an unreliable sign.
Is my puppy growing too fast or too slow?
Every 2–4 weeks, compare your puppy’s weight with the table the calculator gives you. Small differences are normal. Call your vet if your puppy:
- stops gaining weight for more than two weeks,
- loses weight, or has diarrhea or a poor appetite,
- is gaining much faster than expected and looks round rather than lean (you should be able to feel the ribs easily).
For steady growth, feed a diet made for puppies. Dogs expected to top about 55 lb should get a large-breed puppy food. Then set portions with our dog food calculator.
Frequently asked questions
How accurate are puppy weight calculators?
Usually within about 15% for purebreds weighed after 12 weeks. They’re less reliable for very young puppies, mixed breeds, and dogs whose growth was set back by illness or diet. Treat the result as a range, not a promise.
At what age is a puppy half its adult weight?
Around 4 months for toy and small breeds. Large breeds get there at about 4.5–5 months, and giant breeds closer to 5–6 months.
What age do puppies stop growing?
Between 9 and 24 months, depending on size. Toy and small breeds finish at about 9–12 months, medium breeds at about 12–15 months, large breeds at 15–18 months and giant breeds at 18–24 months. Some large dogs keep filling out with muscle until age two.
How much should an 8 week old puppy weigh?
It varies hugely by breed. Toy puppies may weigh 1–3 lb at 8 weeks, medium-breed puppies around 6–12 lb, and large-breed puppies 12–20 lb. Enter your puppy’s weight above to see if it fits the expected curve.
Does this work for a mixed breed puppy?
Yes. Choose “Not sure” and the calculator picks the growth curve that best matches your puppy’s numbers. If you know the parents’ weights, the dog size calculator will give a better estimate.