Puppy Weight Calculator

How do I use the puppy weight calculator?

1. Weigh your puppy. Kitchen scales work for small puppies; for bigger ones, weigh yourself holding the puppy and subtract.
2. Enter the age in weeks. Multiply months by 4.3 if you only know months (3 months ≈ 13 weeks).
3. Pick the expected adult size. Use the breed’s typical adult weight, or the bigger parent for mixes.
4. If you know both parents’ weights, add them. The calculator then uses their average to choose the size class.
5. Read the range and check the chart. Weigh again every 2–4 weeks and re-run it; the estimate gets tighter.

What formula does the puppy weight calculator use?

The “share of adult weight” comes from growth standards built from US vet clinic records; the researchers screened data on more than six million young dogs and kept healthy dogs that stayed in ideal body condition (Salt et al., 2017). The researchers made separate curves for five size groups up to 40 kg (88 lb). We read the middle line of each curve and turned it into a share-of-adult-weight table. The giant row is our own extension, because the published standards stop at 40 kg.

How is the calculation done?

With the default example, a 12 lb puppy at 12 weeks that should be a large dog:

1. Pick the size class. A puppy expected to be a large dog (33–66 lb adult) uses the large-dog growth curve.
2. Look up the share of adult weight at 12 weeks for that class: 0.30 (30%).
3. Divide current weight by that share: 12 lb ÷ 0.30 = 40.0 lb.
4. Add a range of ±15% because puppies vary: 34–46 lb.
5. Check the answer lands in the class you picked: 40 lb is inside 33–66 lb, so the curve fits. If it didn’t, you’d switch class and recalculate.
6. Estimate when growth slows: large dogs reach about 90% of adult weight around week 43 (about 10 months).

Worked example: a small-breed puppy at 16 weeks

Your Miniature Schnauzer puppy weighs 8 lb at 16 weeks. Small breeds (14–20 lb adult) are around 53% grown at that age, so 8 ÷ 0.53 = 15.1 lb. With a ±12% range, expect about 13–17 lb, which sits inside the usual range for the breed. Small dogs grow fast early, so most of that growth is done by about 7 months.

Are puppy weight calculators accurate?

Honestly, only roughly, and anyone who promises a single exact number is guessing. Three things limit accuracy:

• Young puppies vary a lot. Before about 14 weeks, small differences in weight turn into big differences in the prediction.
• Size class is a guess. For mixed breeds you’re estimating the class, and the prediction depends on it.
• Curves describe the middle. Healthy puppies can track above or below the middle line their whole lives.

What helps: weigh on the same scale, re-run the calculator every few weeks, and look at the trend. A puppy that keeps crossing growth lines up or down is worth mentioning to your vet (Salt et al., 2020 found crossing lines was linked to becoming overweight or underweight).

Want the full week-by-week expected weights? See the puppy growth chart. Planning a crate? Size it for the adult with the crate size calculator.

When should you see your vet?

• Your puppy stops gaining weight, or loses weight, for more than a few days.
• Your puppy looks pot-bellied, thin or has poor appetite, diarrhea or vomiting.
• Your puppy is growing very fast and is a large or giant breed. Overfeeding raises the risk of joint problems.
• You’re not sure about body condition. Your vet can show you how to check ribs and waist.