How to Calculate Dog Years and Cat Years

If you think you can calculate dog or cat years by multiplying by 7, think again. That’s the OLD way of doing the math.

How do you calculate dog years or cat years?
Happy birthday! (Now, how do you calculate dog years or cat years?)

I have always understood animal years are seven times human years. I can’t remember where I picked this fact up, but it’s stuck with me for most of my life. If you had a dog for one year, he was 7 in dog years. Simple as that.

When you think about it, dogs and cats can start reproducing just months after they are born. Humans can’t reproduce that soon, so it made me wonder how this original calculation was formed. That’s like saying a 1-year-old human can reproduce. Scary, huh?

Dog Aging

Dogs age pretty fast in their first couple of years, but the aging process varies depending on the breed. Larger breeds such as Newfoundlands mature faster but tend to have shorter life spans. Medium and small dogs reach senior status much later in life, around seven  years of age for medium-sized dogs and 10 years of age for toy breeds.

While no true and exact method is available for calculating dog years, veterinarians agree that this is a much better guideline to follow instead of the one times seven method. These new guidelines assume that a 1-year-old dog is equal to a 12-year-old human. The amount doubles after that (a 2-year-old dog is equal to a 24-year-old human), and continue this method adding four years for every age that follows.

This new method takes into account the earlier maturation and slowing toward senior years. The director of veterinary services at Boston’s Animal Rescue League, Martha Smith, agrees that this calculation is a more accurate representation of dog years. Here it is in chart form:


The average life span for dogs ranging in the low teens, but this can vary by breed. Large breeds tend to live shorter lives while medium and small dogs (and females) live much longer.

Cat Aging

The formula for calculating a cat’s age is a little different. Here’s a chart to show how it’s calculated:


Cats live an average of around 15 years (indoors) and 10 years or less (outdoors). Their first year is a little more maturing than dogs, but they catch up at year two.

Looking over these charts has me thinking about my own pets. By these calculations my dog is almost 64-years-old and my cat is a spring chicken at around 15 years old. I hope I look as good as my dog when I reach that age!

Kristine Lacoste

View posts by Kristine Lacoste
Kristine Lacoste, editor in chief of Petful, has been researching dog and cat breeds for nearly a decade and has observed the animals up close at dog shows in both the United States and the United Kingdom. She is the author of the book One Unforgettable Journey, which was nominated for a Maxwell Award from the Dog Writers Association of America, and was host of a weekly pet news segment on the National K-9 Academy Radio Show. In addition, she was the New Orleans coordinator for Dogs on Deployment, a nonprofit that helps military members and their pets, for 3 years. Kristine has researched and written about pet behaviors and care for many years. She holds a bachelor’s degree in psychology, another bachelor’s degree in English and a Master of Business Administration degree.

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