When Is a Dog Considered an Adult? – The Ultimate Guide

Young puppy with mother

A dog’s current life stage plays a significant role in determining the type of care you will need 

to provide. It determines everything from diet and exercise needs to vaccinations and check-up requirements.

To help you figure out when your little puppy has become an adult dog, we put together this comprehensive guide! Read on to learn how you can support your canine companion as they become an adult.

Table of Contents

When Does a Puppy Become an Adult Dog?

The age at which a dog becomes an adult will vary depending on several factors. Most importantly, the dog’s breed and size will determine the age that they can be considered an adult.

For the most part, veterinarians categorize dogs into six main groups – extra small breeds (teacup dogs), miniature breeds (toy dogs), small breeds, medium breeds, large breeds, and giant breeds.

Each of these breed categories will reach adulthood at a different age. Since the categories are weight-based rather than a breed-specific factor, mixed breeds and mutts also fall into these categories.

That said, the weight ranges for each category are based on the dog’s expected adult weight. This means it is easier to determine adulthood if you know what type of dog you have.

Different types of puppies are considered adult dogs at the following ages:

  • Extra Small / Teacup Breeds (8 pounds and under) – 8 months
  • Miniature / Toy Breeds (8 to 15 pounds) – 10 months
  • Small Breeds (16 to 25 pounds) – 11 months 
  • Medium Breeds (26 to 55 pounds) – 12 months
  • Large Breeds (56 to 100 pounds) – 15 months
  • Giant Breeds (101 pounds and over) – 18 to 24 months

What Determines These Adulthood Classifications?

The age when your dog is considered an adult is linked to the growth phase for each type of dog. The larger the dog is, the longer it will take for that dog to reach physical maturity.

This is why the smaller breeds reach their adult life stage faster than the large breed dogs.

How Can You Support Your Puppy as They Approach Adulthood?


For your puppy to develop into a healthy adult, it is important to support them in the following ways: 

Meet Their Unique Dietary Needs

If you have ever owned a puppy, you know they grow incredibly quickly. One moment, they are tiny puppies tripping over their paws. The next moment, they are full-sized adult dogs.

All of this rapid growth requires a specialized diet. Puppies need significantly more calcium in their diet than adult dogs. This is because their skeletons are still developing.

They also require a diet that is very rich in high-quality protein. The rapid growth of body tissue, especially muscle, means their bodies need dietary protein to develop healthily. 

Overall, the food needs to be very dense in calories and nutrients. Frequent meals filled with high-quality nutrients that are easy to digest will help support your puppy’s journey into adulthood.

Ensure They Are Physically Fit

Ensuring your puppy gets plenty of physical and mental stimulation will also help them become a happy and healthy adult.

With that said, you do not want to over-exercise your young puppy. This can strain their growing bodies and do more harm than good.

A general rule is to take your puppy’s age in months, then multiply that number by five. This will help you determine how long your puppy’s walks should be. You can take your dog for a walk of that length twice a day.

For example, you can walk a 5-month-old puppy for 25 minutes twice a day. This is because 5 months x 5 = 25 minutes.

Make Sure Their Vaccination Requirements and Checkups Are Met

It is also important to ensure your dog has all of its required vaccines at the appropriate ages. 

Since the region where you live and your dog’s breed determine your dog’s vaccination needs, it is important to speak with a veterinarian about a care plan for your specific dog.

Once you know your puppy’s vaccination schedule, you can begin scheduling obedience and socialization classes. When all your young dog’s vaccines are up-to-date, you can take your pup to the local dog park.

Your veterinarian will also explain when your puppy should be spayed or neutered. It is better to take care of this procedure while your dog is still young, as complications are more common in adult dogs.

When Can You Switch from a Puppy Diet to an Adult Dog Diet?


Once your dog has reached its full adult size, you can transition them to adult dog food. While the age guideline listed above can be useful, you can also speak with your veterinarian. This will help you know for sure when your dog finishes growing.

Diet is important during a dog’s puppy life stage, but this does not mean it is unimportant once the dog is an adult.

Ensuring your adult dog gets a nutritionally balanced diet made from high-quality ingredients is incredibly important. An adult dog’s short-term and long-term health are influenced by their diet.

How to Transition a Puppy to Adult Dog Food

Sudden changes in diet are not a good idea with any dog. The sudden change can be a shock to their digestive system. 

Once your dog is an adult, slowly introduce them to adult food over several weeks. Mix some of the adult kibbles into their puppy food. Gradually increase the amount of adult dog food they receive.

This is very important if switching your dog from wet puppy food to dry kibble. Even when introducing the food gradually, the dog may still suffer from diarrhea for a few weeks. 

Speak with your veterinarian about a diet plan that matches your dog’s specific needs. As you would expect, different breeds have different nutritional and caloric needs.

For More Information

If you want to know more about diet plans for adult dogs, we recommend reading the American Kennel Club’s thorough guide to canine nutrition – How to Choose the Best Dog Food.

FETCH is an online pet-care resource that was created by WebMD. They have a guide to canine life stages that can also be a useful resource for dog owners – Puppy to Dog: Your Pet’s Life Stages.

Finally, for more information about caring for your pooch as it approaches adulthood, we recommend reading Caring For Your Puppy from the Royal Society for the Prevention of Cruelty to Animals (RSPCA).

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