Puppy Weight Calculator – How Big Will My Puppy Get?
Puppies grow at different speeds depending on their eventual size. Enter your puppy's age and weight for an adult estimate, shown as a sensible range.
Estimated adult weight
10.2 kg – 13.8 kg
Most likely about 12 kg
Size category: Medium
Fully grown: around 12 months
Crossbreeds are harder to predict – adding the parents' weights helps.
Expected growth curve
How puppy growth prediction works
Puppies of different sizes grow on very different timetables. A Chihuahua is half its adult weight at twelve weeks and finished by its first birthday. A Great Dane is only a quarter of the way there at twelve weeks and may still be filling out at two years old. So rather than one rule for every dog, we use a completion curve for each size category and work backwards from where your puppy is today.
Worked example: a 16-week medium-breed puppy
Say a Cocker Spaniel cross weighs 6 kg at sixteen weeks. Medium breeds are about half their adult weight at that age, so 6 ÷ 0.50 gives an estimate of 12 kg. Allow the usual fifteen per cent either side and the sensible range is roughly 10.2 kg to 13.8 kg. If you also know mum weighed 13 kg and dad 15 kg, the parent average of 14 kg nudges the estimate up.
Typical completion milestones
- Toy and small: 50% at 12 weeks, 60% at 16 weeks, 80% at 6 months, done by 12 months.
- Medium: 40% at 12 weeks, 50% at 16 weeks, 70% at 6 months, done by 12 months.
- Large: 33% at 12 weeks, 45% at 16 weeks, 60% at 6 months, done by about 18 months.
- Giant: 25% at 12 weeks, 33% at 16 weeks, 50% at 6 months, still filling out at 24 months.
Why crossbreeds are trickier
A Cockapoo can come from a toy poodle or a standard poodle, and the difference in adult size is enormous. The same goes for Labradoodles, Cavapoos and Pomskies. If you know the parents' weights, enter them – it is by far the most useful extra piece of information. Otherwise, treat the range as genuinely wide rather than fixating on the middle number.
Feeding a growing puppy
Puppies under four months need around three times their resting energy requirement, dropping to twice from four to twelve months. Large and giant breeds should be kept lean and fed a large-breed puppy food with controlled calcium; growing too fast is linked to joint problems. Weigh your puppy weekly to start with, plot it, and expect a smooth curve rather than sudden jumps.
When to check with your vet
Speak to your vet if your puppy is not gaining weight week on week, has a pot-bellied appearance with a dull coat, or is far outside the expected range for their breed. Those can be signs of worms, poor diet absorption or an underlying condition, and they are all easier to sort out early.
Frequently asked questions
How big will my puppy get?
Divide your puppy's current weight by the share of adult weight they have reached at their age. A medium-breed puppy is about half grown at 16 weeks, so a 6 kg puppy is heading for roughly 12 kg.
How accurate is a puppy weight calculator?
For a purebred puppy of known age it is usually within about 15 per cent. Crossbreeds are harder to predict because they can take after either parent.
When is a dog fully grown?
Small dogs are done by around 12 months, medium dogs by 12 months, large dogs by 18 months and giant breeds can keep filling out until 24 months.
Do the parents' weights help?
Yes. For purebred puppies, the average of the mother's and father's weights is a strong guide, and we blend that with the growth-curve estimate when you enter them.
Does neutering affect adult size?
Early neutering can delay growth plates closing, which sometimes makes dogs slightly taller. Discuss timing with your vet, especially for large breeds.
My puppy looks skinny. Is that normal?
Growing puppies often look leggy and lean. You should be able to feel ribs easily but not see them prominently. Ask your vet to body-condition score at the next vaccination.
Should I feed a large-breed puppy food?
For puppies expected to reach 25 kg or more, yes. Controlled calcium and energy help joints develop properly.
Estimates only – not a substitute for advice from your vet.
Last reviewed: 22 September 2026