Puppy Weight Calculator
Updated
Quick answer
How big will my puppy get?
A medium puppy at 16 weeks is about half its adult weight, so double it. A large puppy doubles from 20 weeks, and a giant puppy at 16 weeks is only about a third grown. For any other age and breed size, divide current weight by the typical percent grown below; the calculator does it for you.
| At 16 weeks | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| % grown | 62% | 57% | 50% | 40% | 34% |
How to predict your puppy's adult size
Three inputs predict adult size well: current weight,age, and expected breed size. At any given age, puppies of a given breed size have typically reached a known fraction of their adult weight, so dividing today's weight by that fraction gives the estimate1. A 12-pound, 4-month-old medium puppy is about 50% grown: 12 ÷ 0.50 = 24 pounds of eventual dog.
What moves the answer most is the breed size, which is why the calculator asks for it instead of a breed name. Parents are the best clue; for shelter mysteries, a DNA test settles it, and the mixed-breed section below covers the guesswork in between.
Puppy growth chart: percent of adult weight
Find your puppy's age and breed size; the cell is how much of their adult weight they've typically reached. Divide current weight by it for the estimate.
| Age (months) | Toy | Small | Medium | Large | Giant |
|---|---|---|---|---|---|
| 2 | 33% | 30% | 25% | 22% | 17% |
| 3 | 51% | 46% | 40% | 32% | 27% |
| 4 | 66% | 61% | 53% | 43% | 37% |
| 5 | 79% | 74% | 63% | 53% | 46% |
| 6 | 88% | 83% | 72% | 62% | 54% |
| 9 | 100% | 97% | 90% | 80% | 71% |
| 12 | 100% | 100% | 100% | 92% | 83% |
| 15 | 100% | 100% | 100% | 100% | 92% |
| 18 | 100% | 100% | 100% | 100% | 100% |
We computed this table with the same growth curves the calculator uses, anchored to published growth standards12. 100% means typical maturity for the breed size; individual dogs spread around every number here.
The 16-week rule (and its size fixes)
The rule of thumb everyone repeats says to double a puppy's 16-week weight. It's a medium-dog rule: at 16 weeks a medium puppy is about half grown, so doubling lands close. The size fixes: toy and small puppies are already past halfway at 16 weeks (double them and you'll plan for a dog that never arrives), large breeds double from about 20 weeks, and a giant puppy at 16 weeks is only about a third of the final dog. Use the calculator's fraction instead of the folklore and the math sorts itself out.
Mixed-breed puppies
Good news: this method never needed a breed name. Pick the breed size you expect from the parents (mom is usually the better-known half) and the same growth math applies. If the parents are a mystery, watch the trajectory instead: weigh every two weeks, run the number each time, and the estimates will converge on the truth by 4 to 5 months. A DNA test is the shortcut when you'd rather know than wait.
When do puppies stop growing?
Skeletal growth ends when growth plates close, and that happens on a size schedule3:
| Breed size | Full-grown around |
|---|---|
| Toy (<10 lb / 4.5 kg) | about 9 months |
| Small (10–20 lb / 4.5–9 kg) | about 11 months |
| Medium (20–50 lb / 9–23 kg) | about 12 months |
| Large (50–90 lb / 23–41 kg) | about 15 months |
| Giant (90+ lb / 41+ kg) | 18 months or more |
Dogs keep filling out with muscle after the skeleton finishes, so a "done growing" dog can still gain healthy weight for months. Once they're grown, the dog age calculator takes over the birthday math.
How it works
Puppies grow along a predictable curve: fast at first, slower every month, until the growth plates close. If you know how far along that curve your puppy is today, then today's weight points straight at the destination. That's all this calculator does.
The growth-fraction method: at each age, puppies of a given breed size have typically reached a known percentage of adult weight. The calculator interpolates that percentage from size-specific growth curves and divides your puppy's current weight by it. Anchors follow published growth standards12 and veterinary guidance on maturity ages3.
The range moves the growth fraction six percentage points each way, which honestly covers most individual variation. Estimates are least certain before 12 weeks and sharpen with every weigh-in after.
The math is unit-agnostic: enter pounds and get pounds, enter kilograms and get kilograms.
Frequently asked questions
How accurate is a puppy weight calculator?
It's an estimate, and the range is the honest part. Breed size, nutrition, genetics, and neuter timing all shift the outcome, which is why we show the likely range alongside the single number. The estimate sharpens as your puppy ages: a 4-month weigh-in predicts far better than an 8-week one.
How big will my puppy get at 6 months?
By 6 months, a toy or small puppy is nearly done growing (about 85 to 90% of adult weight), a medium puppy is about three-quarters grown, and a large or giant puppy is only just past halfway. Big dogs are marathoners.
Is the 16-week rule true?
For medium dogs, yes: at 16 weeks a medium puppy is about half its adult weight, so doubling works. Large breeds hit the halfway point closer to 20 weeks, and giants later still. The calculator applies the right fraction for each size automatically.
Do big paws mean a big dog?
Only loosely. Paws proportionally ahead of the body hint at growth still to come, but coat, breed mix, and individual variation fool everyone, vets included. Current weight at a known age predicts far better than paws ever will.
Is this the same as the AKC puppy weight calculator?
The approach is the same family: breed-size growth curves. Ours shows the working (the exact growth fraction used), gives a likely range instead of a single number, and works for mixed breeds without needing a breed name.
Does neutering change how big a puppy gets?
It can. Neutering before growth plates close is associated with slightly taller adult height in large breeds, and weight is then steered mostly by feeding. Timing is a genuine vet conversation, especially for large and giant breeds.
Can I predict adult size from birth weight?
Not usefully. Litter size and early nursing dominate birth weight, and the correlation with adult size is weak. From 8 weeks on, the breed-size method starts working; from 16 weeks, it works well.
References
- 1.Salt C, et al. (2017). Growth standard charts for monitoring bodyweight in dogs of different sizes. PLOS ONE 12(9). journals.plos.org
- 2.WALTHAM Petcare Science Institute. Puppy Growth Charts. waltham.com
- 3.American Kennel Club. When Do Dogs Stop Growing? When Are Puppies Fully Grown? akc.org
