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PawCurve

Puppy Weight Calculator

Enter your puppy's age and weight to predict its adult size — using growth curves we computed ourselves from 8.5 million real veterinary weight records, with the error range shown rather than hidden.

For a mixed breed, guess from the parents if you can. Not sure? Leave it on medium — we show how much the answer moves either way.

Sex

Predicted adult weight

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Most likely range —

That range is an 80% interval. On 63,993 dogs we held back from fitting, the real adult weight landed inside it 79.9% of the time.

Growth percentile now
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Expected to finish growing
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Curve used
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Growth chart showing your puppy plotted against weight percentiles for dogs of the same adult size and sex
Shaded bands are the 3rd–97th and 25th–75th percentiles of real dogs of this adult size and sex. The dot is your puppy; the open circle is the prediction.
Month-by-month: what your puppy should weigh as it grows
AgeExpected weight% of adult size

This follows your puppy's own percentile, not the average. It is what a dog tracking this growth line typically weighs at each age.

What the result actually means

The prediction works by finding the growth percentile your puppy is on today, then following that same percentile forward to the age its size group finishes growing. A puppy at the 70th percentile at 10 weeks usually becomes a dog at roughly the 70th percentile — which is a far better assumption than pretending it will grow at this week's rate all year, but it is still an assumption. Puppies drift between percentiles. That drift is exactly what the range is measuring.

So read the range, not the single number. We publish an 80% interval, which means about one dog in five lands outside it — and that is the honest shape of this problem, not a flaw we could engineer away. Any puppy calculator that gives you one confident number and no range is not more accurate than this one. It is just not telling you.

Accuracy also depends on size. Big dogs are easier to predict in percentage terms: median error is about 12–13% for medium, large and giant breeds, versus about 19% for toy breeds. A toy breed being 1 lb off is a much bigger fraction of a 7 lb dog than 1 lb is of a 90 lb dog.

Why we don't use the "× 52" formula

The formula you'll find on most puppy weight calculators is adult weight = current weight ÷ age in weeks × 52. It is simple, it is easy to implement, and it is wrong in a specific, measurable way: it treats growth as a straight line when growth is a curve that flattens out.

We were able to quantify exactly how wrong, because the dataset lets us check predictions against what the dogs actually grew into. Across 63,993 held-out dogs, that formula missed by a median of 45% and was biased 43% too high. The damage is worst where the marketing is loudest — on small dogs. For toy breeds it overshoots by about 82%, so a Chihuahua owner is told to expect roughly double the dog they will get.

This isn't a hypothetical complaint. It is the formula sitting behind a large share of the puppy weight calculators you can find today.

Want the whole chart instead? This page predicts your puppy's adult weight. If you'd rather look up what's typical at each age, the puppy growth chart has the full percentile curves and a week-by-week table for every adult size — built from the same 8.5 million records.

Frequently asked questions

How accurate is this puppy weight calculator?
We measured it, which is not something puppy weight calculators normally do. Predicting from a puppy's weight at 8–12 weeks, the median error was 15%, and the real adult weight fell inside our stated range 79.9% of the time. That was measured on 63,993 dogs that were held out of the fitting entirely, so it is not the calculator grading its own homework. Accuracy is better for bigger dogs (median error about 12–13%) than for toy breeds (about 19%), because toy breeds vary more in proportion to their size.
Why is your answer different from other puppy weight calculators?
Most of them use one line of arithmetic: current weight ÷ age in weeks × 52. That assumes a puppy keeps growing at today's rate for a whole year. Puppies don't — they grow fastest early and then taper off, which is why the formula overshoots. We tested it against the same 63,993 dogs: it missed by a median of 45% and ran 43% too high. On toy breeds it was 82% too high — it will roughly double a Chihuahua. We follow the puppy's actual growth percentile through real measured growth curves instead.
How big will my 8-week-old puppy get?
At 8 weeks a puppy is typically about 25% of its adult weight if it's a toy breed, but only about 12% if it's a giant breed — we measured this directly from the data, and it's why "multiply by X" rules of thumb fall apart across sizes. Eight weeks is early, so the honest answer is a range rather than a number. Worth knowing: the published growth charts most sites cite only start at 12 weeks. The underlying data doesn't stop there, so we extended our curves down to 6 weeks and this calculator will answer for an 8-week-old.
Does neutering change how big my puppy gets?
It can. Neutering before a puppy finishes growing delays the growth plates closing, which tends to make a dog slightly taller rather than heavier. Our curves are built from a population that includes both neutered and intact dogs, so this variation is inside the range we quote rather than something we predict separately. Timing of neutering is a real conversation to have with your vet, especially for large breeds — it's not something a calculator should decide.
My puppy is off the chart. Should I worry?
Not necessarily. Someone has to be at the 3rd percentile and someone at the 97th, and both can be perfectly healthy — percentile is not a grade. What matters more is the trend: a puppy that has been tracking the 60th percentile and drops to the 20th is worth a vet visit, even though both numbers are "normal". A one-off reading also just wobbles — puppies weigh more right after a meal. If your puppy seems off in any other way, ask your vet rather than a website.
Can I use this for a mixed-breed puppy?
Yes, and mixed breeds are a genuinely good fit for this method, because it works from adult size rather than breed identity. Pick the adult size you expect from the parents. If you have no idea, try the calculation at two different sizes — the gap between the answers tells you how much your uncertainty about the parents actually costs you, which is more useful than a single confident-looking number.
What data is this built on?
Growth curves computed by us from the raw dataset behind Salt et al. (2017), Growth standard charts for monitoring bodyweight in dogs of different sizes, PLoS ONE 12(9): e0182064 — released under CC BY 4.0. It holds 14,957,947 weight measurements from 3,475,842 dogs. We didn't trace the published figures; we went to the raw records and recomputed, which is why we can show error bars and go below 12 weeks. The full method, including where we deliberately departed from the paper and why, is on our methodology page.

Related

Method and data sources last reviewed 2026-07-17. See methodology for the full derivation, including the checks that failed.