When Do Dogs Stop Growing? Ages by Size and Breed

Most small dogs reach their adult weight by 8 to 12 months, while larger breeds can keep growing until they're about two years old. The bigger a dog is going to be, the longer it usually takes to fill out. Regular weigh-ins with your vet, plotted on a growth chart, are the best way to see where your puppy is along the way.

The short version

• Small dogs usually reach adult weight by about 8 to 12 months.
• Larger breeds can take up to about 24 months.
• Growth charts exist for dogs, built from the records of more than 6 million young dogs, in five size categories.
• Healthy puppies tend to follow their own growth line. A puppy that keeps crossing lines is worth a vet check.
• Neutering timing shifts growth only slightly, less than the normal differences between dogs.
• Genes set the target size: a handful of size genes explain much of the difference between breeds.

How long dogs grow, by size

The best large-scale evidence comes from a 2017 study that built growth standards for dogs from the veterinary records of more than 6 million young dogs. It describes very small dogs reaching maturity between 8 and 12 months of age, and larger breeds needing up to 24 months to reach adult body weight.

The study also found that growth could be described by size category rather than needing a chart for every breed. Its five categories are based on a dog's predicted adult weight:

The standards cover puppies from 12 weeks to 2 years old and don't apply to dogs heading for more than 40 kg. If you have a giant-breed puppy, ask your vet how they'll track its growth.

Growth slows before it stops

Puppies put on weight fastest in their first months, and growth slows as they approach adult size. In practice, that means the gain from one weigh-in to the next gets smaller and smaller, until your dog's weight holds steady. That's the sign your dog is close to full grown, as long as its body condition stays in a healthy range.

Watch the growth line, not just the number

Growth charts plot a puppy's weight against lines called centiles. A 2020 follow-up study found that healthy dogs rarely moved across more than two of those lines while growing: fewer than 5% did. Dogs that became overweight by age three had often grown faster than expected and crossed lines upwards, while dogs that became underweight had crossed lines downwards.

So the useful question isn't just "how much does my puppy weigh?" but "is my puppy staying on its line?" If your puppy keeps moving up or down across lines, talk to your vet about feeding and body condition. Our guide to checking whether a dog is overweight covers body condition at home.

What affects when a dog stops growing

• Genetics: a 2007 study found a single version of the IGF1 gene common to all small breeds and nearly absent from giant ones, and later work found that variants near six genes explain about half of the size differences between breeds.
• Neutering timing: the 2017 study found neutering before 37 weeks was linked to a slight upward shift in growth, and after 37 weeks to a slight downward one, both small compared with the normal differences between dogs. Talk to your vet about timing.
• Food and health: the growth standards were built from healthy dogs kept in ideal body condition through their first three years, so feeding and health both matter.

How a DNA test fits in

A DNA test can estimate how big your dog is likely to be from its genes. The PuppyGenes report includes an estimated adult height and weight: useful context, not a promise. Our guides to whether DNA can predict adult size and estimating a mixed-breed puppy's size explain how to use it alongside your vet's growth checks, and our guide to DNA testing a puppy covers when to swab.