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How Can You Determine Your Dog’s Age?

Wondering how old your dog is? We can help! Here’s how you can determine your dog’s age.

by Naomi Strollo, RVT, CPDT-KA, | March 25, 2024

How Can You Determine Your Dog’s Age?

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If you’re considering adopting a rescue dog, you’ll likely know little about their history. But like any pet parent, you are probably wondering about their past — whether it be their breed ancestry or their age. Determining breeds has become a little easier with DNA tests, but age is a bit more involved. If you have a puppy, there are a few clear signs to help you make an age determination. But with older dogs, that may require more detective work.

There are a number of clues that can be used to estimate a dog’s age, but the accuracy of the guess may be anywhere from close to the truth to wildly off. Why? Like people, each dog visibly ages at a different rate. And a dog’s size, breed makeup, and past health and activity level affect how they age. Here are a few techniques you can use to estimate your dog’s age.

Signs of aging in dogs

It can be pretty tricky to accurately guess the age of an adult dog you’ve adopted. But if your BFF looks the same as the day you adopted them, they were likely pretty young — under three — when you got them. If they’re showing a bit of wear and tear, they’re probably a bit older. There are several physical and behavioral signs to help you determine your dog’s age.

Physical signs of aging

Here are some physical indicators of aging in dogs:

  1. Puppy teeth: One of the most prominent ways to determine a dog’s age is through their teeth. When puppies are young, they have baby teeth that fall out and get replaced in a predictable pattern according to their age. So if you want to know how old a pup is, you can check their teeth. After about six months, most dogs will have all their adult teeth, and then you can’t get an exact age from their teeth.

  2. Adult teeth: As dog’s age, their teeth show signs of wear and tear and appear flatter. They may even develop gum disease. By age four, they may have tartar buildup and yellowing.

  3. Their eyes: Another “tell” indicating a dog’s age is lens clarity. Lenticular sclerosis is a common age-related change in dogs’ eyes that results in a blue or cloudy appearance. It doesn’t affect vision like cataracts do. Almost every dog will develop this condition around nine years old.

  4. Their body: Puppies that are less than a year old have loose skin and round bodies. This extra skin gives them room to grow as they get older. Older dogs tend to lose muscle, develop fat pads in their lower back area, and their spine becomes more prominent.

  5. Graying fur: Graying fur is less of an indication, because some dogs may start getting silver locks when they are only a few years old — while some older dogs may still have their original color. Studies have shown that many young dogs experience premature graying due to anxiety and fear. Basically, they get grays when they’re stressed — just like we do.

Behavioral signs of aging

There are even more factors that give insight into a dog’s age. Here are some behavioral signs of aging in dogs:

  1. Energy levels: As a dog ages, their activity levels decrease. A common cause of this change is arthritis. They may walk stiffly, or be slower to sit down and stand up. You may see them play less, and even lay down or walk away in the middle of a game of fetch. 

  2. Hearing: Large dogs will show signs of hearing loss or sensitivity as early as six years of age. Small dogs will show signs by nine years of age. You will start to notice they are not coming when you call them. They aren’t moving out of the way when the vacuum comes close, and they stopped barking at the doorbell. 

  3. Vision: Dogs steadily become more nearsighted as they age. You may begin to notice they don’t want to go into a dark room, or they hesitate going out at night. If you move a piece of furniture, they may bump into it. 

  4. Sleep: You may notice your dogs sleeping more. They are sleeping-in longer in the morning and taking more naps during the day. Puppies and senior dogs require 16 to 18 hours of sleep a day. 

  5. Smell: Over the age of 10, there is a decline in their ability to smell. This can affect their interest in food. You may have to find foods that have a greater odor to increase their interest. 

  6. Bladder: Senior dogs can start leaking urine when they sleep (urinary incontinence). They lose bladder strength and can’t hold it as long as they used to.  

  7. Change in personality: Many senior dogs become more introverted. They desire more alone time. They may avoid affection and not want to be pet or hugged as much as they used to.

Dog life stages

When is a dog considered a puppy?

It’s easy to spot a puppy. A dog is considered a puppy from birth to one year of age, though larger breeds have longer puppy growth periods. Puppy development is divided into five stages: neonatal, transitional, socialization, preadolescence, and adolescence. There are a few signs to look for during each state that can help you tell a puppy's age.

1. Neonatal: The neonatal puppy stage ranges from birth to around two weeks of age. The puppy’s eyes are not open yet, and the ear canals are closed. The puppy experiences the world through touch and smell. 

2. Transitional: The transitional puppy stage begins around two to three weeks of age and lasts only a week or two. During this stage, eyes and ears begin to function, and muscle coordination improves. Playing is first observed during this period. The puppy is able to go potty on their own without the aid of stimulation.

3. Socialization: A puppy’s socialization stage starts at three weeks of age and lasts until 14 weeks. Puppies that have not been socialized during this time have a tendency to react fearfully to new humans and new situations. Controlled exposure to humans during this period is critical. Negative experiences during this period have a profound impact on behavioral development. Abrupt weaning, and removing from their mom’s care before eight weeks of age will cause them to become more fearful and have more undesirable behaviors as adults, which is why you shouldn’t adopt a puppy until they are at least eight weeks of age. 

4. Preadolescence: The preadolescence stage is between three months and six months of age, ending at the onset of puberty. In this stage, puppies begin to explore and show more signs of independence. They also begin to feel more comfortable around people and other dogs when properly and continually socialized. 

5. Adolescence: The adolescence stage starts at six months of age. This “teenage” phase is a hormonal time for both sexual and social maturity. Just like with human teens, their brains are still developing, and they are more impulsive and likely to overreact. They also become more independent and have increased energy levels. During this period, they tend to lose their early puppy training easily, and for example, may have no desire to come to you when called. Adolescence ends around 18 months of age but can go on until two years old depending on the breed or the dog. 

At what age do dogs stop growing?

Growth can be a helpful marker of age. Smaller dogs are usually done growing by one year of age. Large dogs continue to grow until they are two years of age. Once their growth stops, they’re considered adult dogs. Smaller breeds hit adulthood at age one, whereas larger breeds are considered adults at age two. 

One of the biggest factors determining at what age a dog will stop growing is their expected adult size:

  • Small breeds (under 25 pounds) are known for rapid growth, and reach their full-grown size between six to eight months old. 

  • Medium breeds (25 to 50 pounds) reach their full-grown size between 12 and 15 months of age. 

  • Large breeds (over 50 pounds) are slower in their growth process. They aren’t fully grown until 15 to 18 months. 

  • Giant breeds (100 pounds and more) take the longest to reach full size, which is 18 months.  

When is a dog considered a senior?

Detecting when a dog is in their twilight stage is also a bit easier to determine. All dogs are considered senior dogs at eight years of age, but the earliest age at which a dog is considered a senior depends on their size. 

  • Small or toy breeds (less than 20 pounds): 8 to 11 years

  • Medium-size breeds (20 to 50 pounds): 8 to 10 years

  • Large breeds (50 to 90 pounds): 8 to 9 years

  • Giant breeds (more than 90 pounds): 6 to 7 years

Commonly asked questions

How can I find out how old my dog is?

The rescue from which you adopted your dog will have the best clues on how old your dog is. A veterinarian can also help you determine your dog’s age by looking at their teeth, eyes, and overall appearance.

How can you determine a dog’s age?

You can attempt to calculate a dog’s age by looking at their teeth, eye clarity, body condition, movement, and overall appearance. Their breed, health, size, and activity level will also play a role in how they age.

Can a vet tell how old a dog is?

Yes, a veterinarian can provide a general estimate of how old a dog is. However, due to a variety of factors impacting how dogs age, your vet will come up with an estimate rather than a fully accurate number.

How do you determine the age of a female dog?

You can gauge the age of a female dog by looking at the same overall physical appearance as any other dog of the same or similar breed: their teeth, body condition, and eye clarity.

How do you determine the age of a male dog?

Much like with female dogs, you can estimate the age of a male dog by making an assessment of a dog’s body condition: how their teeth look, their eye clarity, their spinal curvature, and fatty deposits.

How can you tell how old a rescue dog is?

Your vet can determine the age of your dog by reviewing their teeth. Puppies gain their permanent incisors between two and five months, their canines around five months, their premolars between four and six months, and their molars by seven months. Puppies tend to lose their teeth starting around 12 weeks, and will typically have their full set of adult teeth when they’re six months old. Their adult teeth typically arrive quickly and orderly, helping to give insight into their age. 

How do you tell how old a stray dog is?

It’s best to take stray dogs to a local veterinarian or animal shelter where they can check for a microchip and determine the dog’s age.


Age Determination in Dogs

Anxiety and Impulsivity: Factors Associated with Premature Graying in Young Dogs

Dog Spine Issues

Eye Health and Canine Cataracts

Inflammatory Pattern of the Infrapatellar Fat Pad in Dogs with Canine Cruciate Ligament Disease

Lenticular Sclerosis in Dogs

Lumbosacral Disease in Dogs

Naomi Strollo, RVT, CPDT-KA

Naomi Strollo, RVT, CPDT-KA

Naomi Strollo R.V.T, CPDT-KA, has been a Registered Veterinary Technician for over 20 years. Working in general practice and emergency medicine. Having special interest in behavior, she went on to become Fear Free Certified, and a Certified Professional Dog Trainer - Knowledge Assessed (CPDT-KA). She has participated in therapy dog, confirmation, and CGC certifications with her dogs. With positive-reinforcement training, her Akita, Pitbull, and Shiba Inu know how to be friends. Living in Ohio, she enjoys sharing her knowledge through writing contributions.