How big will my puppy get? Four ways to guess, ranked by how often they're right
Updated October 31, 2026 · 2 min read · by the PupCurve editorial team
Everyone with a new puppy wants to know. Will it fit on the sofa? Will it still be a lap dog? There are four common ways to guess, and they are not equally good.
1. Paw size
The folk method: big paws, big dog. It isn't useless, since heavy-for-their-age puppies tend to have big paws, but we haven't found good evidence that paw size predicts adult weight better than the puppy's weight does. Puppies also grow into their paws at different rates by breed. Use it for fun.
2. The parents
Better. If you know the mother's and father's weights, their average is a sensible starting point for a puppy of two same-breed parents. It gets shaky when the parents are far apart in size, when one of them is a mix, or when one is unusually heavy or light for the breed. It's most helpful before the puppy is old enough to weigh meaningfully. You can try it in the dog size calculator.
3. The breed standard
Fine for purebreds, with a catch. Breed standards give a range, and the range can be wide. Labradors are listed at roughly 55 to 80 lb. The standard also describes the show-ring ideal, and pet dogs often fall outside it. Think of it as the first guess, then refine it with the puppy's own weight.
4. The puppy's own weight and age
Best, and better the older the puppy gets. Dogs follow a growth curve, and a puppy's weight at a known age tells you how far along it is. We measured how well this works on records from over a million dogs. On puppies held back from the fitting, a single weigh-in at 8 to 11 weeks was off by a median of about 18% of adult weight. At 12 to 15 weeks it was about 15%, at 16 to 25 weeks about 12%, at 26 to 38 weeks about 9%, and at 39 to 52 weeks about 6%.
In plain terms, for a puppy that will weigh 50 lb: a forecast at 10 weeks will typically be out by around 9 lb, and at 6 months by around 4 lb. Still useful, especially when you give it a range, which is what the puppy weight calculator does.
Combine them
The honest answer is to use all of it. Start with the breed or parents, then weigh the puppy every week or two and let the forecast update. A good forecast uses more than one reading, but it doesn't treat three weigh-ins in a row as three independent facts. In our data, the error in a forecast at one age was strongly tied to the error three weeks later, so the third reading adds less than the first.
If your puppy is a mix, the weight route matters most. The calculator can work out the likely size class from the puppy's numbers alone, with a wider range early on.
What not to rely on
- Doubling the weight at some magic number of weeks. It works for some medium dogs at some ages and badly misses others.
- Puppy looks. Coat, leg length and head size change a lot as puppies grow.
- DNA tests as a size oracle. They can tell you ancestry, which helps, but ancestry in a mix gives you a range rather than a number.
Questions people ask
How accurate is predicting puppy size?
On dogs held back from our fitting, a single weigh-in was off by a median of about 18% of adult weight at 8 to 11 weeks and about 6% at 39 to 52 weeks.
Can I tell my puppy's size from its paws?
Only loosely. We haven't found evidence that paw size beats weight as a predictor, so we don't use it.
How do I predict a mixed-breed puppy's size?
Weigh the puppy at a known age and use the calculator with the breed left blank. Add more weigh-ins every few weeks to tighten the range.
At what age is the prediction good?
Usable from 8 weeks, good from about 16 weeks, and quite reliable by 6 months.
Sources
This guide is general information, not veterinary advice. If you're worried about a puppy, call your vet. In an emergency, go to the nearest emergency clinic.