How Long Is a Dog Considered a Puppy?

Your dog is still a puppy until she achieves physical and mental maturity. For most dogs, the end of puppyhood is when she stops growing, usually between 1 and 2 years of age.


Puppies differ from adult dogs both in physical maturity and in their behavior. Although the exact timeframe varies by size and breed, pretty much all dogs are considered adults by 2 years of age.

When Do Dogs Stop Growing?

Scientifically, your dog stops growing when the growth plates in her bones seal up and are no longer creating new bone. This can be seen on an X-ray. Puppies will have black lines toward the ends of all of their longer bones, while adult dogs do not.

The timing of growth-plate closure is controlled by hormones and varies with the size of the dog. Small-breed dogs, under 20 lbs of adult weight, tend to mature more quickly, while large breeds, with a mature weight of over 70 lbs, take the longest. Toy breeds can be done growing around 1 year of age, while giant breeds will continue to grow until their second birthday, and they will continue to “bulk up” for several years after that.

Most medium-size dogs, between 20 and 50 lbs, are done growing around 18 months of age.

How Long is a Dog Considered a Puppy for Food?

Your dog should be eating puppy food until his growth plates close. Those growing bones require a lot of extra nutrients and minerals. It won’t hurt to leave him on the food a little longer, as long as he doesn’t gain excess weight.

General guidelines for when to switch to adult food are:

  • Small dogs: 9 months
  • Medium dogs: 12 months
  • Large dogs: 18 months
  • Giant breeds: 18 to 24 months

Large- and giant-breed puppies should eat food specifically formulated for large-breed puppies to support optimal growth of those big bones. You should feed a food labeled for “Growth/Reproduction” or for “All Life Stages.” If you have a large-breed dog, read the AAFCO nutritional statement on the bag of food, which should state if it is acceptable for puppies who will mature at 70 lbs of weight or more.

Tip: If you’re nervous about when to make the change from puppy food to adult food, you can feed a diet that covers all your bases. All Life Stages foods provide everything that both puppies and adult dogs need. Check out Whole Dog Journal’s approved dry foods and approved canned foods for help sorting among the many different brands of food.

How Long is a Dog a Puppy Mentally?

Puppy brains go through many of the same processes that child brains go through. Your adolescent puppy may have a mostly mature body, but her brain isn’t there yet. Adolescence ends around 18 to 24 months for most dogs.

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Kate Basedow, LVT is a long-time dog enthusiast. She grew up training and showing dogs, and is active in a variety of dog sports. She earned her Bachelors Degree in English from Cornell University in 2013, and became a licensed veterinary technician in New York in 2017. She has been writing professionally about dogs for most of her life, and has earned multiple awards from the Dog Writers' Association of America. Kate currently has three dogs at home, as well as a cat, two zebra finches, and six ducks.