Puppy weight calculator: how big will my puppy get?
A puppy’s adult weight can be estimated from three things: its age in weeks, what it weighs today, and the size class it will grow into. Enter those below and the calculator returns a predicted adult weight, a working range, and—if you pick a breed—a check against that breed’s published adult range.
This is a growth-curve projection from published breed averages, not veterinary advice. Adult weight varies with genetics, neutering age and feeding, and only your veterinarian can say whether an individual puppy is growing as it should.DogBreedCompass does not guarantee the accuracy of any figure or statement here and accepts no liability for how it is used. You are responsible for your own decisions - confirm anything that matters with your veterinarian. Full disclaimer.
How this puppy to dog weight calculator works
The calculator divides current weight by the share of adult weight a puppy has already reached. That share depends almost entirely on adult size class, not on breed: bigger dogs grow for longer and are therefore a smaller fraction of their finished weight at any given week. A 20-week toy puppy is already at 65% of adult weight, while a 20-week giant-breed puppy is only at 38%.
Each size class gets its own curve, anchored every four weeks and interpolated in between, and each curve reaches 100% at the age that class stops growing: 52 weeks for toy and small dogs, 65 for medium, 78 for large, and 104 for giant breeds. The full table is below, so you can do the arithmetic without the tool. The output is then widened by 10% either side, because a single weigh-in cannot capture how much individual dogs vary within a litter.
Percentage of adult weight by age and size class
The table below is the model, in full. Read across to your puppy’s age in weeks, down to its adult size class, and divide the current weight by that percentage. At 24 weeks, for example, a large breed is at 56% of adult weight, so a 34 lb six-month-old Labrador points to roughly 61 lb full grown.
| Age | Toy / small | Medium | Large | Giant |
|---|---|---|---|---|
| 8 weeks | 22% | 18% | 14% | 11% |
| 12 weeks | 40% | 33% | 27% | 21% |
| 16 weeks | 55% | 45% | 38% | 30% |
| 20 weeks | 65% | 55% | 47% | 38% |
| 24 weeks | 75% | 65% | 56% | 46% |
| 28 weeks | 82% | 72% | 63% | 53% |
| 32 weeks | 88% | 78% | 69% | 59% |
| 36 weeks | 92% | 83% | 74% | 64% |
| 40 weeks | 95% | 87% | 79% | 69% |
| 44 weeks | 97% | 90% | 83% | 73% |
| 48 weeks | 99% | 93% | 86% | 77% |
| 52 weeks | 100% | 95% | 89% | 81% |
| Fully grown at | 52 weeks | 65 weeks | 78 weeks | 104 weeks |
Curve anchors: 12 points for toy and small dogs, 15 for giant breeds. Values between anchors are interpolated linearly.
What this estimate cannot tell you
Treat the output as a planning range, never as a target weight. The model knows nothing about your individual dog: it cannot see body condition, neuter status, or whether the puppy was weighed before or after a meal. Those three factors alone move a single reading by several percent, and the error compounds when you divide by a small fraction early on.
Sex and body condition are not modelled, and that is deliberate rather than an oversight. The published breed ranges this page checks against already span both sexes, so splitting the curve by sex would need per-breed data nobody publishes. Adding an input we could not back with a source would make the answer look more precise without making it more accurate.
Three specific limits are worth naming. First, estimates made before 12 weeks are the least reliable, because dividing by a fraction near 0.2 magnifies any weighing error fivefold. Second, mixed-breed puppies can inherit either parent’s adult size, so the size class you choose matters more than the arithmetic. Third, early neutering delays growth-plate closure in large breeds, which tends to produce a slightly taller, lighter adult than the curve predicts.
Re-run the calculation every four weeks. Successive estimates that agree with each other are far more trustworthy than a single reading, and a prediction that keeps drifting upward or downward is a signal to check food portions with your veterinarian rather than to adjust them yourself.
Puppy weight questions
How much will my puppy weigh as an adult?
Divide your puppy's current weight by the share of adult weight its size class has reached at that age. A 16-week medium-breed puppy is usually at 45% of adult weight, so a 12 lb puppy points to roughly 27 lb grown. The calculator above does that division for you and adds a 10% band either side, because littermates from the same litter routinely finish 2-4 lb apart.
Is a dog weight calculator by breed more accurate than one by size?
Slightly, and only because the breed gives a second reference point. The growth curve itself is driven by adult size class, not by breed, so a Beagle and a Cocker Spaniel of the same adult weight follow the same curve. What the breed adds is the published adult weight range, which lets the tool flag an estimate that lands more than 25% outside it.
Can I use a dog size calculator on a mixed-breed puppy?
Yes, but pick the size class you expect the adult dog to land in rather than the one it looks like today. Mixed-breed puppies are the case where the estimate spreads widest, since paw size and current weight are weak predictors. If you genuinely do not know the mix, run the calculation twice, once for medium and once for large, and plan for the wider range.
When do dogs stop growing?
Small and toy dogs finish at about 12 months, medium dogs at about 15 months, large dogs at about 18 months, and giant breeds keep filling out until roughly 24 months. Height is reached before weight in every size class: the growth plates close first, then the dog broadens through the chest for several more months.
What to do with the number
Once you have a predicted adult weight, use it to buy gear once instead of twice. The crate, collar and harness size charts convert an adult weight straight into a crate length and a collar range, and the dog cost calculator turns it into a food and vet budget for your city.
More dog calculators and charts
Every tool on this site is free, runs in your browser, and uses the same breed dataset. Nothing you type is saved or sent anywhere.
- Dog age calculatorConvert dog years to human years using the size-adjusted scale, and see the full 1-to-15-year conversion table for small, medium, large and giant dogs.
- Dog crate, collar and harness size chartsCrate lengths, collar neck sizes and harness chest sizes by weight, plus the recommended crate size for every breed in our database.
- Breed size comparisonPut two or three breeds side by side and compare adult weight, shoulder height and typical lifespan on the same chart.
- Dog food calculatorDaily calories, cups per day and meals per day from your dog's weight and life stage, using the published resting-energy formula and the calories per cup on your own bag.
- Puppy starter plannerA first-30-days plan for a new puppy, built from its breed, age, your home and your schedule: what to do in what order, what to buy, and what the month costs.
- Dog body condition scoreScore your dog on the 9-point body condition scale from three hands-on checks, see the full chart, and find out whether it is carrying the right amount of fat for its own frame.
- Dog cost calculatorCheck whether a monthly budget realistically covers a given breed in a given US city, including first-year and ongoing costs.
- Breed cost comparisonCompare first-year and monthly cost ranges for two breeds side by side, adjusted for city cost of living and vet pricing.
- Dog treat calculatorWork out the 10 percent of daily calories that treats are allowed, then turn that ceiling into a number of the treats you actually buy.
- Dry matter basis calculatorConvert the guaranteed analysis on any dog food label to a dry matter basis, so a wet food and a dry food can be compared on the same footing.
- Dog food cost per calorieCompare foods on cost per 1,000 kcal rather than price per bag, which is the only comparison that survives different kibble densities.
- Dog crate size calculatorMeasure the dog, add the published 3-to-4-inch allowance, and get the minimum interior crate height and length - plus a per-breed height table.
All dog calculators and size chartsBrowse all 66 breed profilesTake the breed match quiz