An adult Welsh Corgi dog resting with its puppy.

When Is a Dog Considered an Adult?

Many dog owners wonder: When is a puppy considered an adult? Life stages impact how the pet owner feeds, trains, and exercises their pet. The truth, however, isn’t all that simple.

There isn’t a specific age at which a dog is suddenly an adult. The transition to adulthood is gradual and involves physical growth, hormonal changes, and behavioral development.

Breed size plays a major role, with small dogs maturing more quickly than large and giant-breed dogs, but there’s still variation, even within a specific breed. Here, we’ll answer your common questions about the transition from puppyhood to canine adulthood.

Q1: When is a dog considered an adult?

There isn’t an exact dog maturity age at which a dog is considered an adult. Instead, adulthood is based on physical growth, hormonal maturity, and the dog’s behavioral development.

Most dogs will reach physical adulthood between 1–2 years of age, but the timing varies by breed and size. By “physical adulthood,” we tend to mean that the rapid growth phase is complete and that the dog has reached hormonal maturity if they’re still intact.

There are differences in small vs. large breed maturity. Small-breed dogs tend to mature quickly, often reaching physical adulthood before they’re a year old, while some giant-breed dogs may not be physically mature until they’re around 2 years old.

A dog can also look full-grown before they’ve reached mental maturity. For this reason, dogs can be considered to have a “young adult” stage while they continue to mature behaviorally. According to the Association of American Animal Hospitals (AAHA), the normal dog development stages include puppy, young adult, mature adult, senior, and end of life.

Q2: How does breed size affect maturity?

Small breed dogs under 20 pounds usually reach physical adulthood by the time they’re 9–12 months old, though some reach maturity closer to 6 months.

Medium breed dogs ranging from 20–50 pounds may reach adulthood closer to a year of age. Some may become adults prior to a year of age, but it’s common for them to be closer to 12–15 months old, especially dogs at the higher end of this weight range.

Large-breed dogs (50–90 pounds) usually reach adulthood at over a year of age, often when they’re 15–18 months old.

Giant breeds (90+ pounds) tend to take the longest to reach physical maturity. While this usually occurs between 18–24 months of age, it’s possible for it to take over 2 years.

It’s important to understand that there’s a lot of variation, and even dogs within the same breed may not mature at the same time. Your dog’s size and whether they’ve reached physical maturity will impact their exercise requirements. High-impact exercise can have negative effects on the joints of growing puppies. Make sure to speak with your veterinarian about what’s best for your dog and whether they need any exercise restrictions as they grow.

Q3: What signs show that a dog is becoming an adult?

The following are signs that a dog may be moving out of puppyhood into adulthood:

It’s common for dogs to reach physical maturity before they’re mentally mature. Your dog may continue to display some puppy behaviors even after they’re considered an adult. This is normal. It can take several years for a young dog to settle down and have a more calm, predictable disposition.

Q4: When should I switch my dog from puppy food to adult food?

Most puppy food bags list the age to switch to adult food as 1 year of age, but it’s better to base when to switch on your dog’s physical maturity. Small breeds may make the switch around 9–12 months of age while large breeds may be closer to 18 months of age.

Puppy food is important for your dog’s growth, and switching too early can affect their development. This is especially important in giant-breed dogs, who may do best with a puppy food specifically designed to support growth in large-breed puppies.

For breed-specific guidance, owners should consult their veterinarian.

Q5: Does spaying or neutering affect when a dog becomes an adult?

While spaying or neutering doesn’t really change when a dog reaches adulthood, it can influence the dog’s behavior and growth. Early spay or neuter may delay the closure of growth plates in large-breed dogs, which may contribute to orthopedic problems. For this reason, many veterinarians recommend delaying spay and neuter in large or giant dogs until they’ve reached physical maturity.

If altered early, the dog is also less likely to display sexual behaviors. Some dogs may continue to display territorial marking or mounting behaviors.

There isn’t a uniform recommendation for when to spay or neuter your dog. Much like transitioning to an adult diet, it’s best to speak with the pet’s veterinarian to determine what is best for the individual dog.

Q6: When do dogs reach emotional or behavioral maturity?

Dogs usually reach physical maturity before they reach emotional or behavioral maturity. For most dogs, adolescence will cover the time from 6–18 months of age. During this time, the dog will test boundaries, and their behavior may not be consistent. Some dogs will continue to mature emotionally until they’re closer to 3 or 4 years of age.

Pet owners should continue the dog’s training, provide the pet with adequate exercise, and maintain a routine throughout adolescence and young adulthood. In most cases, “teenage dog behavior” is temporary. Pet owners should keep in mind that dogs do have a range in activity levels and behaviors, as well. Some dogs will remain high energy well into their senior years.

Consult with Your Vet

Although most dogs reach physical maturity between 1–2 years of age, the transition from puppyhood to adulthood depends heavily on the dog’s breed and body size. Physical development will often precede behavioral maturity. Pet parents should consult with their veterinarian to ensure they’re meeting their growing dog’s nutritional, exercise, and training needs. With patience, consistency, and veterinary guidance, a puppy’s maturation can be a rewarding part of raising a happy, healthy dog.