Puppy Weight Calculator

A rough planning guide, not veterinary advice. Your vet can track your puppy's growth curve.

How to use this puppy weight calculator

1. Weigh your puppy and enter the weight. You can use pounds, kilograms, ounces or grams, and the result is shown in the same unit.
2. Enter the age in weeks or months. Estimates are best from about 8 weeks.
3. Pick the expected adult size group. If you are not sure, use the parents' sizes or ask your breeder or vet. For a mixed breed, pick the group that best matches the likely size.
4. Read the estimate and the range, and check which rules were used.

How do I estimate my puppy's adult weight?

This calculator uses several well-known rules of thumb. None of them is exact, and the result is clearest when a rule fits both the age and the size group.

Rule	When it applies
Weeks formula: weight ÷ age in weeks × 52	A general starting point for any size from about 8 weeks
Weight at 8 weeks × 3	Small and toy breeds, about 7 to 9 weeks old
Weight at 16 weeks × 2	Medium and large breeds, about 14 to 18 weeks old
About half of adult weight at 4 to 5 months	Common rule of thumb, about 16 to 22 weeks old
About two-thirds grown at 6 months	Medium breeds, about 24 to 28 weeks old

When a size-specific rule applies, the calculator uses it for the estimate and shows the weeks formula as a cross-check. If none applies, it uses the weeks formula alone. The range is 15% either side, because puppies do not grow in a straight line.

Worked examples

Small breed: a 4 lb puppy at 8 weeks gives 12 lb by the ×3 rule, with a range of about 10 to 14 lb. The weeks formula gives 26 lb, which is much too high for a small breed, and is a good example of why size matters.

Medium breed: a 20 lb puppy at 16 weeks gives 40 lb by the ×2 rule and the half-weight rule, a range of about 34 to 46 lb.

Weeks formula at a glance

Estimated adult weight from the simple weeks formula (not adjusted for size):

Age	5 lb now	10 lb now	15 lb now	20 lb now
8 weeks	33 lb	65 lb	98 lb	130 lb
12 weeks	22 lb	43 lb	65 lb	87 lb
16 weeks	16 lb	33 lb	49 lb	65 lb
20 weeks	13 lb	26 lb	39 lb	52 lb
24 weeks	11 lb	22 lb	33 lb	43 lb

When do puppies stop growing?

Growth speed depends on size. Small and toy breeds grow quickly and usually reach adult size by around 9 to 12 months. Medium breeds usually finish between 12 and 15 months. Large and giant breeds grow more slowly for longer, often 18 months or more. Weight can keep changing after the frame is full-grown as the dog fills out.

Weighing a puppy accurately

• Weigh at the same time of day, before a meal, on the same scale.
• For small puppies, a kitchen scale in grams or ounces is more accurate than a bathroom scale. For bigger dogs, weigh yourself with and without the puppy and subtract.
• Write down the date and weight each week so you can see the trend.

Why the estimate can be wrong

Adult size is mostly inherited, so the parents are a better guide than any formula, and a mixed breed with unknown parents has a wide range. Illness, parasites and feeding change weight without changing the frame underneath. Under eight weeks, puppies gain weight too quickly for these rules to mean anything. Use the result to plan a crate, a food budget or a harness size, not to judge whether your puppy is healthy. That is a question for your vet.