A Critical Exploration of “Dog Years”—What Do Vets Say?

Party hats not included.

dog years

If your lovable Shiba Inu is 6, then that means they’re roughly the equivalent of a 42-year-old human… Right?

Chances are, you’ve found yourself wondering what your dog’s age translates to in “dog years.” Everyone has heard the simple calculation: Multiply a dog’s age by seven, and that equals an age in “dog years.” 

Sorry to break it to you, but this handy trick doesn’t really give all that much accurate info about your dog’s aging or maturity level. 

Where did that “seven years” rule come from?

Throughout history, people have wanted to understand more about their companion animals, including how they age.

Way back in 1268, an inscription into the floor of Westminster Abbey in the United Kingdom explained when the end of the world would come through the lifespans of various animals, including the dog. This carving is part of the Cosmati Pavement, whose elaborately tiled and inscribed flooring notes that dog’s have a lifespan of 9 years, while people have a lifespan of 80. This 9:1 ratio is thought to be the first recorded instance of weighing a dog’s age against a human’s age. 

Flash forward to 1953, when a French scientist named A. Lebeau was busily researching dogs and aging. He argued that, in a dog’s first year of life, they age 15 to 20 times faster than a human being. Then, in a dog’s later years, that rate slows down, according to Lebeau.

The American Kennel Club notes that the “seven dog years to one person year” gained traction in the 1950s. The 7:1 ratio may have come from the oversimplification that dogs live about 10 years and people live about 70 years. 

It’s unknown exactly how the equation was first developed or why it became so popular and widespread, despite the lack of scientific basis behind it. It’s simply one of the myths about dogs that persists to this day, regardless of facts to back it up. 

dog years
To Pepper, age is just a number.

The myth of seven years

It’s true that dogs age faster than we do, but the “seven years” concept doesn’t actually align with the reality of how dogs age and what we know about them.

Dr. Melissa Berg of the NorthStar VETS Emergency and Critical Care team explained that the idea of seven dog years to one human year is flawed. “The general concept is correct—dogs do age more quickly than their humans,” she says. “But the seven-to-one ratio is simplistic and outdated.” 

For dog owners wanting to better understand their dogs, there isn’t really an exact formula for how dogs age in comparison to people. 

Yes, dogs age at a rate much faster than people do, but “there is great variation amongst the breeds of dogs, especially in size,” Berg notes. “There is a strong correlation between adult body size in dogs and longevity. In general, larger breeds tend to age more quickly and have shorter life expectancies. Smaller breeds have greater longevity. Medium breeds, on average, fall somewhere in-between, in respect to aging and life span.” 

One of the easiest ways to point out the fallacies of the “seven dog years to one human year” myth is by considering reproduction. Dogs can get pregnant as soon as they reach sexual maturity. For some dogs (generally small breeds) this can be at six months of age, or even slightly younger. When you apply the seven dog years to one human year it becomes obvious how little sense this equation makes. 

Understanding aging 

In thinking about how dogs age in relation to people, Dr. Antje Joslin, veterinarian for Dogtopia, explains that there are some calculations that can be made.

“For the average medium-size dog the first year of their life is equivalent to the first 15 years of a human [life],” Joslin says. “So, when they hit one-year-old, they are squarely a teenager.” 

Dr. Joslin goes on to explain that for a healthy, medium-sized dog, their second year of life amounts to about nine human years, bringing them to around 24-years-old right before their third birthday. Then, every year after that adds another 5 human years.

dog years
Sunny celebrating her 2nd (or is it 14th? 24th?) birthday.

Being aware of breed traits when it comes to development and aging is important. It’s another reason why dog owners should avoid relying on any simplistic “dog age calculator.” 

An individual dog’s genetics, breed, size, and health will all play contributing roles in how long a dog will live. 

“The breed differences in respect to aging become more pronounced over time,” Dr. Berg says. “For instance, a 6- or 7-year-old toy breed is likely to have the appearance and activity level that they enjoyed as a younger adult. Large and especially giant breed dogs are considered seniors as they enter this age bracket, and may be noted to have graying muzzles and arthritic changes to their joints, as well as other aging changes.”

The outliers

Toy breeds and giant breeds of dogs throw off even the best equations. The smallest of dog breeds reach physical and mental maturity much earlier than medium or large breed dogs.

“Some giant breed dogs, like Great Danes and Bernese Mountain Dogs only live 7 to 9 years, while some other breeds may live well into their late teens” explains Dr. Joslin. Although they have shorter life spans, these giant dogs tend to have slower mental and physical development than small dogs. In fact, many giant breeds aren’t fully grown, physically and mentally until after their second birthday.

Dog aging and training considerations 

From a training perspective, it’s essential to be aware of canine aging and development.

When puppies and adolescent dogs are still growing and filling out their bones, they are still developing. Too much exercise (like running and jumping) before growth plates have closed can lead to serious injuries—and even life-long orthopedic issues. 

Similarly, even though your large-breed dog might look like an adult, they are still mentally immature and developing. If owners aren’t aware of this, they can easily expect too much from their large breed puppies simply because they look like they are adults, when developmentally they are closer aligned to a much younger small- or medium-sized puppy.

dog years
Schnitzel enjoying his birthday cake.

Increasing lifespans 

Although smaller dogs tend to live longer than their larger canine counterparts, this isn’t something that you can take for granted. 

“Even though we do see these aging differences, we cannot assume that our larger breed dogs are doomed, and our smaller breeds will automatically live to a ripe old age,” warns Dr. Berg. 

Just like with humans, a dog’s genetics as well as their lifestyle will play a contributing role in how long they live.

“There is much we can and must do with proper diet, appropriate preventative care, and addressing changes early before they become established problems,” encourages Dr. Berg. She also notes that “each dog needs to be treated as an individual, but keeping these aging differences in mind can help guide us in health screening, tailoring diets to life stage, and monitoring for diseases and conditions that can be associated with age at the appropriate times for each pet. This, in part, is based on their breed and size.” 

Thanks to modern medicine, the average lifespan of dogs continues to increase. From high-quality dog food options, to preventative veterinary care, dogs are being better cared for than in past generations, and that means many are living longer. 

The growth and expansion of comprehensive and specialized veterinary care including cancer treatments, orthopedic surgeries, early diagnostics, and physical therapy means that dog owners can keep their pups healthy and comfortable for longer than dogs of the past.

Predicting the future

There is no crystal ball or exact way to predict how long a dog will live. However, gaining as much knowledge about your dog as possible can be beneficial for a long and healthy life. 

If your dog came from a responsible breeder, ask about the genetic testing they have done on your dog’s parents and relatives prior to breeding. Dr. Joslin advises that instead of getting caught up in a dog aging formula, dog owners should instead “read up on life expectancy and common health issues for your dog breed. If you have a mixed breed, genetic tests are easy and readily available. They can give you some fun and useful insights into your dog’s genetics and life expectancy.” 

For centuries people have tried to understand how our canine best friend’s age. Although there is no scientific basis for that 7:1 dog year calculation, it’s so widely known that people continue to rely on it. 

There is truth to the fact that dogs develop and age faster than we do. Even with all the advancements in veterinary care, unfortunately, a dog’s lifespan is shorter than our own. 

The good thing is that dogs exist in the here and now. They aren’t worried about how fast they are aging, and they’re not anxiously Googling equations online, trying to figure out how old they are compared to us.

Dogs live in the moment, and there’s no calculation that can tell us how long we will have with them at our side. With that in mind, maybe we all should put down our calculators and go play with our dogs. 

Sassafras Lowrey

Sassafras Lowrey CPDT-KA, CTDI is a Certified Professional Dog Trainer (CPDT-KA), Certified Trick Dog Instructor (CTDI) and award winning author. Sassafras’ books have been honored by organizations ranging from the American Library Association to the Dog Writers Association of America and the Cat Writers Association. Sassafras’ books include: Healing/Heeling, Bedtime Stories for Rescue Dogs, Tricks in the City, and Chew This Journal. Sassafras lives and writes in Portland, Oregon. Learn more at sassafraslowrey.com.


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