A 2019 study debunked the 7-year rule.

Girl with Dog on Kitchen Floor
Credit: Getty/Stephanie Rausser

Remember when you used to calculate your dog’s age in human years by multiplying by seven? It’s not quite so straightforward these days. A recent study has led scientists to a new formula for uncovering Fido’s relative age in human years, but there are a few things you should know first.

Perhaps the biggest piece of the puzzle when it comes to this newfangled idea of life expectancy is that their age is largely tied to their genetic makeup. It’s long been acknowledged that larger dogs tend to age faster than smaller dogs for a variety of reasons still somewhat unknown by scientists. According to the American Kennel Club, scientists have determined that each 4.4 pounds of body mass results in a decrease life expectancy of one month. Using that methodology, they created an easy-to-follow chart that shows just how old your dog is based on its relative size.

Now on to how they came up with those numbers.

In 2019, a team of researchers at the University of California San Diego compared the epigenetic clock (a new concept for determining age based on genetic factors) of 104 Labrador Retrievers to that of humans. It was decided that each year of a dog’s life (older than one) is equal to the result of multiplying the natural logarithm of their age (use this calculator) by 16 and then adding 31 to the total. Of course, you can skip the math and go straight to Science magazine’s Dog Age Calculator or revisit that chart provided by the AKC. In fact, we wholly support going either of those routes, especially if you haven’t had your coffee yet.

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Another way to calculate roughly the same number is by considering the first year of a medium-sized dog’s life equivalent to 15 human years, with each subsequent year counting for 5 human years.