An adult Welsh Corgi dog resting with its puppy.

When Is a Dog Considered an Adult?

A question many pet parents ask is, “At what age is a puppy no longer considered a puppy?”

There are no hard and fast rules for canine adulthood. Becoming an adult dog depends on the size, breed, and genetic line of an individual dog. All pups have their own unique requirements and that can influence when they become an adult. In this article, we will consider the different factors that influence maturity and when to change a dog’s diet from puppy food to adult food.

At What Age Is a Dog an Adult?

The 1-year mark is typically when most dogs transition from puppyhood to adulthood. However, there are also some subtle variations based on breed and size. Even dogs within the same litter can grow at different rates. In general, small breeds mature more quickly than large breeds. Toy or small-breed dogs may be considered adults at 9 months, while large breeds are often not considered adults until 18 months of age. Some giant dog breeds will continue to have bone development until almost 2 years of age.

How Do Size and Weight Influence Maturity?

In general, many believe dogs are “adults” when they reach 80 to 90% of their adult weight. But how do you know the common adult weight of your dog if they’re a mixed breed? One way to evaluate development is to assess for the signs of maturity.

8 Signs of Dog Maturity

The signs of maturity in dogs include the following:

Loss of Baby Teeth

Normal canine growth and development includes getting 28 deciduous teeth (baby teeth) by around 6 weeks of age. Baby teeth start to fall out around 16 weeks of age and adult teeth come in by 6 months of age.

Relaxed Demeanor

Puppies have tons of energy and love to play. For example, puppies will chew on your shoes, get into the trash, pick up and carry sticks in the yard, and play with just about anything around the house. With physical and emotional maturity, dogs tend to focus more on specific toys and calm down in general.

Eating Less

Puppies are very excited about their food and tend to eat a lot. As dogs age, they’re typically less excited about mealtime (though this depends on the individual dog) and eat a bit less.

Less Destructive Behavior

Puppies explore the world with their mouths and can be very destructive. They also chew more while teething, which occurs from 6 weeks to 6 months.

Development of the Adult Coat

The adult haircoat starts to come in after 6 months, with a maturing coat developing between 9 and 18 months. This can vary with the breed or breed mix.

Sexual Maturity

Most dogs reach sexual maturity sometime around 6 months of age. Female dogs have their first heat cycle between 6 and 8 months of age and male dogs will also start to take an interest in female dogs around this time. Breeding is also possible at this point.

End of Growth

Dogs do most of their growing during their first 6 months. Maturity depends on the size of the dog, with many small and miniature-breed dogs reaching adult size by 9 – 12 months and large and giant breeds reaching adulthood between 12 and 24 months.

Fewer Accidents

It is estimated that puppies can hold their urine one hour for every month they’ve been alive plus one. For example, a 2-month-old puppy can hold their urine for about 3 hours and a 3-month hold puppy can generally hold their urine for 4 hours. As dogs mature, they can hold their urine for longer and have fewer accidents.

Caring for Your Dog’s Changing Needs

Requirements for food, exercise, and vet care change as a puppy reaches adulthood. Some examples include:


Changing your dog food from puppy food to adult dog food depends on the size and breed. Small-breed dogs change from puppy to adult food between 9 and 12 months and large-breed dogs change closer to 12 months or later.


Young dogs have lots of energy, which makes playtime critical for physical and mental health. Puppies generally need at least 1 hour or more of exercise per day depending on the dog. Older dogs generally need less exercise, especially as they approach their senior years.

Dog Supplies

Supply needs change based on behavior, size, and growth rate. Dogs can outgrow their collars, clothes, toys, and beds. Durable chew toys are important for aggressive chewers and should be a size that cannot be swallowed. Bigger dogs need bigger toys. The collar should be loose enough to get two or three fingers between the collar and neck. Large-breed dogs may need new supplies a few times as they grow.

Vet Care

For normal, healthy dogs, the bulk of costs occur within the first year, including the puppy vaccine series, deworming medication, and spay or neuter surgeries. Vaccines are required every 3 to 4 weeks until 20 weeks of age, after which vaccines are yearly.

Frequently Asked Questions (FAQs) About When a Dog Becomes an Adult

When Do You Change a Dog’s Diet from Puppy to Adult Food?

Generally, you change from puppy food to adult food when a dog is close (within 85 to 90%) to their full adult weight.

When Is a Dog Fully Grown?

Large-breed dogs are fully grown between 12 and 24 months and smaller-breed dogs less than 50 pounds are fully grown when they are 1 year of age.

At What Age Does a Puppy Become a Dog?

This occurs between 12 and 24 months.

At What Age Does a Puppy Start Acting Like a Mature Dog?

This is an interesting question, since physical and emotional maturity are very different. Some dogs can act like an adult dog at 9 months, while others never emotionally mature.

When Does a Dog Stop Growing?

Small-breed dogs stop growing around 9 to 12 months, large breeds between 12 and 18 months, and giant breeds between 14 months and 2 years.

Puppy Maturity Table

It is helpful to know what to expect from your maturing puppy at various milestones. Here is a list of links to help you as your puppy grows:

What to Expect from Your Puppy at…

When Does “Puppy Energy” Go Away?

When a puppy starts acting like an adult and quiets down depends on the dog. There are some 6-month-old dogs that are very subdued, while other dogs can still have that “puppy energy” well into their senior years.

When Do Dogs Mature and Calm Down?

Emotional maturity depends on the specific dog. As a human analogy, there are some 18-year-old humans that are very mature and other 40-year-olds that have a hard time growing up. Dogs can be the same way. Some mature quickly and others very late or never. In general, most dogs will start to calm down between 12 and 18 months of age.

Is a 2-Year-Old Dog Still a Puppy?

A 2-year-old dog is considered a young adult dog.

At What Age Does a Dog Become an Adult?

Most dogs less than 50 pounds are at their adult size at 1 year, while dogs that are large or giant become adults anywhere between 18 months and 2 years.

How Long Is a Dog Considered a Puppy?

Most dogs are considered a puppy for the first year of life, although they can act like puppies for longer.

What Is Considered Mature for a Dog?

The word mature means “fully developed physically; full-grown.” Physically, this occurs between 9 and 12 months for small-breed dogs and between 12 and 24 months for large and giant-breed dogs. Emotionally, this can be earlier or later depending on the personality of the dog. Small-breed dogs are considered senior dogs at 11 years of age and large and giant breeds at 7 to 8 years of age.

How Old is My Dog Compared to Me?

Comparing dog and human ages has been a long-standing topic of conversation. Find out more here.

How Much Does It Cost to Have a Puppy?

Besides the cost of the puppy itself, the first year of care and supplies can range from $800 to $2000 easily without unexpected problems. Costs include veterinary exams, vaccines, deworming medications, flea/tick/heartworm prevention, and pet supplies such as bowls, food, beds, leashes, collars, spay and neuter surgery, and more.

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