It's Complicated

Are Dog Years Actually Real? What Experts Say About That Old 7:1 Ratio

Plus, one vet offers some very promising insight about future pet longevity.

When you bring a pet home, they become a cherished member of your pack (usually pretty quickly!). After all, few things are as pure in this world as the love of a loyal, happy pup or a snuggly kitten. But one of life's greatest injustices is the too-short lifespan of our pets because, for most of us, there just could never be enough time spent with our furry companions.

We know that dogs, in particular, age rapidly, with the common belief holding that one human year is equivalent to seven dog years. You might even jokingly call your pet's terrible twos their "teenage years" or lovingly dote on your golden oldie before they reach double digits. But is the 7-to-1 ratio a real thing, and is there a way to tell exactly how old your beloved pet actually is?

Debunking Dog Years

Turns out, vets and pet experts have been trying to debunk the "dog years" myth for decades. And that's because it's "a bit of an oversimplification and a little outdated," as Dr. Rebecca Greenstein, B.Sc., D.V.M., and member of Rover's Pet People Panel, tells Scary Mommy.

"Just like us, dogs experience aging with a surprising amount of individual variation," Greenstein explains. "Factors like genetics, size, breed, health status, medical history, diet, level of activity, and overall lifestyle all play a role in determining longevity. It's important to note that some dogs, especially giant breeds, may show signs of aging relatively early, while others might appear or behave like younger dogs well into their senior years."

What's more, there are hundreds of canine breeds, generally averaging between the ages of 8 and 16. Simply put: "Eight years in one breed is not equivalent to eight years in another," as David J. Waters, associate director of Purdue University's Center on Aging and the Life Course, told The Wall Street Journal in 2008.

Big Dogs = Big Love

For example, big dogs bring big love, which makes it all the more difficult when we have to say goodbye to them sooner than we'd like. Why is this, exactly? "We are just starting to unlock some of the secrets of aging in dogs; many aspects of it remain a mystery. Large dogs grow at a significantly faster rate than smaller dogs or people, which might be linked to their accelerated rate of aging and higher rates of cancers."

In a 2013 study published in the journal The American Naturalist, German evolutionary biologist Cornelia Kraus noted that large dogs age as if "their adult life unwinds in fast motion," much as we'd like to hold onto them as long as we possibly can.

Breaking It All Down

So, where did the whole "dog years" thing even come from, and is it actually possible to calculate your pet's age? "The idea came about many decades ago when the average human lifespan was estimated to be roughly 70 years, and the average lifespan for a dog was about 10 years; hence the 7:1 ratio," Greenstein explains. "In reality, there's a lot more complexity to any canine aging calculation."

Generally speaking, the American Veterinary Medical Association calculates as follows:

  • 15 human years equals the first year of a medium-sized dog's life
  • Your dog's second year equals about nine human years
  • Things vary after that, but each human year would be approximately five years for a dog

Your vet can help you make a more educated guess based on your pup's current health, explains Greenstein. "A few methods to utilize to help determine your dog's age include assessing their teeth, examining their coat and paws, checking their eyes, and evaluating their energy levels, muscle mass, and general mobility," she adds. "For a more in-depth investigation, a vet may rely on bloodwork or imaging like X-rays to help detect age-related changes in body systems."

Cat parents, here's the 411 for you: "Both dogs and cats have accelerated aging in the first few years of life," says Greenstein. "Some people estimate that their two or so years of life is equivalent to feline adolescence/early adulthood. After that, they age somewhere between 4 and 7 years for every calendar year. Obviously, these calculations are not a perfect science and depend on a variety of factors."

Slow Claps for Science

We're not gonna mince words here: It's a f*cking bummer that we have such precious few years with our pets. But Greenstein does offer a glimmer of hope.

"Aging in dogs is a hot topic these days in the scientific research community," she says. "In the coming years, we will have a richer understanding of more of the factors that lead to aging and can expect to have breakthrough drugs on the market to extend canine longevity." Until then, we'll just have to love on our pets every chance we can while we've got 'em.