Puppy Growth Calculator: How Big Will My Puppy Get?
Under 14 weeks, multiply your puppy's current weight by about 3. Between 15 and 19 weeks, multiply by 2.5. From 20 weeks, multiply by 2. That's the age-based method our calculator uses, and it gets you a workable ballpark for crate size, harness size and food budgeting.
It is an estimate. Mixed breeds in particular can land well outside it, and no formula on the internet beats knowing what the parents weighed.
Use the Puppy Growth Calculator, enter current weight and age in weeks, and it applies the right multiplier.
The age-based multipliers
| Puppy age | Multiplier | Example: 4kg puppy |
|---|---|---|
| 14 weeks or under | × 3 | About 12kg as an adult |
| 15 to 19 weeks | × 2.5 | About 10kg as an adult |
| 20 weeks or older | × 2 | About 8kg as an adult |
A rough age-based rule. It does not know your puppy's breed, so treat the result as a range rather than a number.
The size-class method, which is usually more accurate
If you know roughly what size class your dog will fall into, breed-appropriate rules of thumb do better than a single age multiplier, because small and large breeds grow on completely different timelines.
| Size class | Adult weight | Rule of thumb | Examples |
|---|---|---|---|
| Toy | Under 5kg | Weight at 6 weeks × 4 | Chihuahua, Pomeranian, Toy Poodle |
| Small | 5kg to 10kg | Weight at 12 weeks × 2 | Jack Russell, Mini Dachshund, Cavalier |
| Medium | 10kg to 25kg | Weight at 14 weeks × 2.5 | Kelpie, Border Collie, Staffy, Beagle |
| Large | 25kg to 45kg | Weight at 6 months × 2 | Labrador, German Shepherd, Golden Retriever |
| Giant | 45kg and up | Weight at 6 months × 2, then keep filling out | Great Dane, Mastiff, Newfoundland |
Widely used rules of thumb, not veterinary formulas. Parent weights beat all of them.
Small dogs finish growing fast and early. Giant breeds are still filling out at two years old. Applying a small-breed rule to a Great Dane puppy will badly undershoot, and applying a giant-breed rule to a Cavoodle will badly overshoot.
When each size class stops growing
| Size class | Height mostly done by | Weight mostly done by |
|---|---|---|
| Toy and small | 8 to 10 months | 10 to 12 months |
| Medium | 10 to 12 months | 12 to 15 months |
| Large | 12 to 15 months | 15 to 18 months |
| Giant | 16 to 18 months | 18 to 24 months |
The distinction that matters here is height versus weight. Growth plates close and height stops first. Muscle and body mass keep filling in for months afterwards, which is why a 12-month-old Labrador looks lanky and a 2-year-old looks like a Labrador.
Why mixed breeds break the maths
A Cavoodle can come from a toy poodle or a standard poodle and land anywhere between 5kg and 20kg. An Oodle of any kind is a coin toss. Same for bitsers from the pound where nobody knows the parents.
Three things that improve the estimate:
- Ask about the parents. Adult weight of the mother and father is by far the strongest predictor. A registered breeder will tell you.
- Look at the paws and legs. Rough and unscientific, but a puppy with paws way out of proportion to its body has more growing to do.
- DNA test. Australian dog DNA kits return a breed mix and usually a predicted adult weight range. They cost real money but they're more useful than guessing, especially for a rescue.
What you actually need the number for
Crate and bed size
Buy for the adult dog, not the puppy. A crate divider lets you shrink the space during toilet training and expand it as they grow, which is cheaper than buying twice.
Harness and collar
Don't buy for the adult size here. A loose harness is a dog that slips out of it on Bondi Beach. Expect to buy two or three sizes across the first year for a medium or large breed.
Food budget
Adult weight drives daily food volume for the next decade or more. A 5kg dog and a 40kg dog are a difference of hundreds of dollars a year on food alone, before you get to worming, flea treatment and medication doses, which are also weight-based.
Rentals, strata and council
Some strata by-laws and rental agreements set weight or size limits on pets. Pet rules differ between states and have changed in recent years in several of them, so check the current rules for your state and your specific building. Council registration fees also vary by council and by whether the dog is desexed.
Travel
Airline pet travel is priced by crate size and combined weight. A 35kg dog in a large crate is a very different quote to a 6kg dog under the seat.
Feeding a large breed puppy: the thing worth knowing
Growing too fast is a real problem in large and giant breeds. Overfeeding a Great Dane or Rottweiler puppy, or feeding a standard adult food with the wrong calcium balance, is associated with orthopaedic problems as they develop.
Large-breed puppy foods are formulated for slower, steadier growth for exactly this reason. If your puppy is heading past about 25kg as an adult, ask your vet about the right food and the right growth curve, rather than aiming for the biggest puppy possible.
Judge condition, not just the scales
Vets use a body condition score, usually 1 to 9, with 4 to 5 as ideal. You can check it at home:
- You should be able to feel the ribs easily under a thin layer of fat, without pressing hard
- From above, there's a visible waist behind the ribs
- From the side, the belly tucks up rather than running straight
A puppy tracking above the predicted weight but with a good body condition score is probably just going to be a bigger dog. A puppy tracking on target but carrying too much condition is a different conversation.
When to stop trusting the estimate
Get the vet involved rather than the calculator if your puppy is losing weight, not gaining for more than a week or two, appearing much smaller than littermates, or has a sudden change in appetite. Growth problems in puppies are worth checking early.
Related tools
- Puppy Growth Calculator for the adult weight estimate
- Dog Food Calculator for daily portions once you know the adult size
- Pet Cost Calculator for the real lifetime cost of the dog
- Dog Years Calculator for the human-years comparison
- Dog Chocolate Toxicity Calculator for the emergency nobody plans for
Frequently asked questions
How do I estimate my puppy's adult weight?
Multiply current weight by about 3 if the puppy is 14 weeks or younger, by 2.5 between 15 and 19 weeks, and by 2 from 20 weeks. Size-class rules are usually more accurate if you know the breed: small breeds double their 12-week weight, large breeds double their 6-month weight.
At what age do puppies stop growing?
Small and toy breeds finish height at around 8 to 10 months and weight at 10 to 12 months. Medium breeds finish at 12 to 15 months. Large breeds take 15 to 18 months, and giant breeds keep filling out until 18 to 24 months.
Why is my mixed breed puppy's estimate so unreliable?
Because a mixed breed can inherit either parent's size. A Cavoodle from a toy poodle and one from a standard poodle can end up 5kg or 20kg. Knowing the adult weight of both parents is the strongest predictor, and a dog DNA test will usually return a predicted adult weight range.
Should I feed a large breed puppy differently?
Yes. Growing too fast is linked to orthopaedic problems in large and giant breeds, which is why large-breed puppy foods are formulated for slower, steadier growth. If your puppy will pass about 25kg as an adult, ask your vet about the right food and growth rate.
Is my puppy the right weight?
Body condition matters more than the number. You should be able to feel the ribs easily under a thin layer of fat, see a waist from above, and see the belly tuck up from the side. A puppy above the predicted weight with good body condition is probably just going to be a bigger dog.