Determining a Pet’s Age in "Human" Years

Published Dec. 22, 2011

The world’s oldest living dog (according to the Guinness Book of World Records) died earlier this month. He lived in Japan, his name was Pusuke, and he was 26 years old. According to his owner, he was eating well and staying active until the day of his death. He died peacefully, surrounded by his loved-ones.

Pusuke was a mixed breed dog. From his picture I’d guess a Chow cross, which doesn’t surprise me since I’ve met both some seriously old Chows and some seriously old mutts in my time. Twenty-six is pretty amazing, though. There isn’t any one formula for determining exactly how old this is in human years, but this is the method I use with my clients.

At the end of your dog’s first year, he is a teenager, 15 or so; by the end of his second year he’s in his mid-twenties, let’s say 24 years old. For the next three "human" years you can add four "dog" years, so that would make him 28 at 3, 32 at 4, and 36 at 5.

Then things get more complicated, because large dogs have shorter life expectancies than do small dogs. I switch to multiplication at this point. Take your dog’s age in human years (as long as he is 6 or older) and multiply it by 5.5 for small dogs, 6 for medium dogs, 6.5 for large dogs, and 7.5 for giant breeds. This would make a 10-year-old dog 55, 60, 65, or 75, depending on his size. At 14 years they would be 77, 84, 91, and 105 respectively, which seems about right to me.

Of course there are always outliers like Pusuke. According to my calculations, as a medium-sized dog he would be 156 "human" years old. That doesn’t seem too plausible, does it?

And according to the Guinness Book of World Records:

The greatest reliable age recorded for a dog is 29 years 5 months for an Australian cattle-dog named Bluey, owned by Les Hall of Rochester, Victoria, Australia. Bluey was obtained as a puppy in 1910 and worked among cattle and sheep for nearly 20 years before being put to sleep on 14 November 1939.

OK, 29 times 6 is 174. Maybe my calculations need a little more work!

Cats are easier. Again, I say they are 15 after one year and 24 at two. Then I simply add four "cat" years for every one "human" year. So at 10 they are 56 and at 20 they are 96. According to Guinness, the oldest cat that has ever lived died at the age of 38. That would put her at 168 years old — wow!

What is the longest you’ve ever known a cat or dog to live?

Dr. Jennifer Coates

Image: Birthday Dog by parl / via Flickr

Jennifer Coates, DVM


Jennifer Coates, DVM


Dr. Jennifer Coates is an accomplished veterinarian, writer, editor, and consultant with years of experience in the fields of veterinary...

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