Puppy Weight Calculator

How big will my puppy get? Get a rough estimate of your puppy's adult weight in kilograms from its weight at 6 weeks, 8 weeks or about 4 months, using a common rule of thumb, then see when puppies of each size stopped growing in a published study. Free, no sign-up.

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Puppy Size Predictor

Estimate how big your puppy will get

Current weight: 5 kg

0.5 kg40 kg

Current age: 16 weeks (about 3.7 months)

6 weeks52 weeks

Estimates work at 6 weeks, 8 weeks, and 16 to 18 weeks (about 4 months).

~10 kg

estimated adult weight

Small dog (about 5.5 to 11 kg)

In a 2004 study, small breeds reached 99% of their adult weight at about 9.5 to 11 months.

Rule used: weight at 4 months × 2 (medium to large breeds), a common rule of thumb, not a veterinary standard.

The 4-month rule is meant for medium to large breeds, so treat it as rougher for a toy or small breed.

This is an estimate from a common rule of thumb, not a veterinary standard (as published by S. C. Mitchell, DVM, PetMD, 2025), and not a guarantee. Mixed breeds and rescue puppies vary the most. Check your puppy's growth with your vet.

How the estimate works

The calculator uses a common rule of thumb, not a veterinary standard. We could not find a vet school, WSAVA, the MSD Veterinary Manual or a peer-reviewed study that publishes a multiplier rule, so we use the version written by Sandra C. Mitchell, DVM, DABVP, in a 2025 PetMD guide to puppy growth:

Toy and small breeds: weight at 6 weeks × 4, or weight at 8 weeks × 3.
Medium to large breeds: weight at 4 months × 2.

Those rules are written for specific ages, so the tool only gives a number at 6 weeks, 8 weeks and 16 to 18 weeks, and tells you when to weigh again at other ages. Doubling only works if the puppy is at about half its adult weight, and research shows that age differs by breed: in a 2004 study of 173 puppies, breeds reached half their adult weight at about 11 weeks (Papillon) up to about 23 weeks (English Mastiff). Other clues the PetMD guide lists are the parents' size, paw size, leg length, body build and sex, and for a firmer answer they can feel the bone structure or check X-rays for closed growth plates.

Treat the result as an estimate. Mixed breeds and rescue puppies vary the most, and your vet can track your puppy's weight against growth charts over time. Researchers have built such charts from the records of healthy pet dogs, covering 12 weeks to 2 years for dogs up to 40 kg (Salt and colleagues, PLoS ONE, 2017).

Puppy growth chart: when do puppies stop growing?

Bigger dogs grow for longer. These are the 12 breeds weighed weekly in a 2004 study of puppy growth (Hawthorne and colleagues, Journal of Nutrition), grouped by size as the study grouped them, with average adult weights. Individual dogs vary, and a 2017 study notes larger breeds can take up to 24 months to reach adult body weight (Salt and colleagues, PLoS ONE).

Size	Breeds studied (adult weight)	Half adult weight at	99% of adult weight at
Toy	Papillon (2.2 kg)	about 11 weeks	about 9.5 months
Small	Cairn Terrier (6.3 kg), Miniature Schnauzer (7.0 kg), Cocker Spaniel (10.2 kg)	about 14 to 17 weeks	about 9.5 to 11 months
Medium	English Springer Spaniel (14.8 kg), Beagle (17.4 kg)	about 14 to 15 weeks	about 9 to 10 months
Large	Labrador Retriever (28.1 kg)	about 19 weeks	about 12 months
Giant	Newfoundland, Great Dane, Irish Wolfhound, St Bernard, English Mastiff (43 to 67 kg)	about 18 to 23 weeks	about 11 to 15 months

Want the breed standards behind each size? See our guides to toy dog breeds, medium sized dog breeds and big dog breeds.

Choosing a puppy by expected size

Mixed-breed and rescue puppies are the hardest to call, so ask the rescue or foster carer what adult size they expect, and about the mother's size if they know it. If you are still deciding between adopting and buying, read puppies for sale: adopt or buy first.

Browse adoptable puppies in Sydney, Melbourne, Brisbane, Perth and Adelaide, or filter by size with small dogs and large dogs in Sydney. Not sure what breed suits you? Try the what dog breed am I quiz.

Caring for a growing puppy

RSPCA Australia advises against both underfeeding and overfeeding puppies, and notes research showing that overfeeding, particularly in large and giant breeds, can predispose puppies to muscle and bone problems. Our dog feeding calculator gives a starting amount, and your vet can adjust it at checkups.

Keep up the vaccination schedule: puppy and kitten vaccinations in Australia.
Settle in with crate training a puppy.
See what a dog of that size costs with the dog cost calculator.

Frequently asked questions

Tap a question to expand

How big will my puppy get?▼

The parents’ size and the breed are the best clues. For a quick estimate, the calculator above uses a common rule of thumb, not a veterinary standard, as published by Sandra C. Mitchell, DVM, on PetMD (2025): for toy and small breeds, multiply the weight at 6 weeks by 4 or the weight at 8 weeks by 3; for medium to large breeds, multiply the weight at 4 months by 2. It is an estimate only, so check your puppy’s growth with your vet.

When do puppies stop growing?▼

Bigger dogs grow for longer. In a 2004 study that weighed 173 puppies of 12 breeds (Hawthorne and colleagues, Journal of Nutrition), toy, small and medium breeds reached 99% of their adult weight at about 9 to 10 months, while large and giant breeds reached it at about 11 to 15 months. A 2017 study that built growth charts for pet dogs (Salt and colleagues, PLoS ONE) notes very small dogs reach maturity at 8 to 12 months while larger breeds can take up to 24 months to reach adult body weight.

How accurate is a puppy weight calculator?▼

It gives a ballpark, not a guarantee. It uses a common rule of thumb, not a veterinary standard, and the rule only applies at set ages (6 weeks, 8 weeks and about 4 months) and to the breed sizes it was written for. Breeds also reach half their adult weight at different ages: from about 11 weeks in a toy breed to about 23 weeks in the English Mastiff in a 2004 study (Hawthorne and colleagues), so a single doubling age cannot fit every dog. Mixed breeds and rescue puppies with unknown parents vary the most. Vets also look at paw size, leg length, body build and sex, can feel the bone structure, and can check X-rays for closed growth plates, so your vet is the best person to confirm the estimate.

Can paw size tell you how big a dog will get?▼

It is one clue, not a measurement. Paw size is on the list of physical traits vets consider in the PetMD guide above, alongside leg length, body build and sex, but feet vary a lot between breeds and between individual dogs. Use it together with the parents’ size, the breed and the calculator’s estimate rather than on its own.

How can I tell how big a mixed-breed puppy will get?▼

Without papers, use the parents’ size if the shelter, rescue or foster carer knows it, the calculator’s estimate at 6 weeks, 8 weeks or 4 months, and your vet’s read of the puppy’s frame. A DNA breed test is another clue the PetMD guide lists. Ask the rescue what adult size they expect.

Does a bigger dog cost more to own?▼

Usually, yes, at least for food. The energy formula in the MSD Veterinary Manual rises with body weight, so a bigger dog needs more food each day. Our dog cost calculator lets you compare the monthly and yearly cost before you commit.

More free tools

General information only, not veterinary advice. The weight estimate is a common rule of thumb, not a veterinary standard. Sources: S. C. Mitchell, DVM, DABVP, “When Do Dogs Stop Growing?”, PetMD (2025), for the rule of thumb and size bands; A. J. Hawthorne et al., “Body-weight changes during growth in puppies of different breeds”, Journal of Nutrition (2004); C. Salt et al., “Growth standard charts for monitoring bodyweight in dogs of different sizes”, PLoS ONE (2017); RSPCA Australia Knowledgebase, “What should I feed my puppy?” (2024).