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Want to know how old your dog is in human years? Forget multiplying by 7

An old dog rests on a broken log of a tree dog-wow
© Pixabay

Since the 1950s we’ve enjoyed telling people how old our dogs are in human years. And in order to do this we have multiplied his age by seven. Not correct, say scientists.

By Nick Whittle , 23 Nov 2019

It’s a bit more complicated, apparently. But old habits die hard. Even yesterday the author found himself calculating the human age of Sam, his 16 year old Yorkie, as 112. This way of determining the equivalent age comes from a standard veterinary calculation of the 1950s: divide the average life span of a human with that of a dog.

However, we now know that aging in dogs is a lot more complicated. A lot of it depends on the dog's breed, size, and environement (like what kind of food they eat, or how much exercise they get). Though each dog ages individually, scientists wanted to end this myth that every dog's human age is basically just their age multiplied by 7.


This month, Science magazine published the results of a study carried out at the University of California that says doing so is not accurate. By studying the epigenetics (genetic changes caused by the environment) of dog DNA, lead researcher Trey Ideker of the University of California has instead come up with a model of aging that is more or less foolproof.

Their studies of comparative aging, including the linking of various milestones of dog and human development such as puberty, old age and disease, culminated in a scientific formula for the calculation of dog age.

The formula

Science magazine writes of the findings of the study: “Dogs’ and humans’ life stages seem to match up. For example, a 7-week-old puppy would be equivalent roughly to a 9-month-old human baby, both of whom are just starting to sprout teeth.

"The formula also nicely matches up the average life span of Labrador retrievers (12 years) with the worldwide lifetime expectancy of humans (70 years). Overall, the canine epigenetic clock ticks much faster initially than the human one.”

Thus, to calculate your dog’s equivalent human age, multiply the natural logarithm of his actual age by 16 and add 31. Simple!

Here's a chart with dog age on the left, and equivalent human age on the right:

1    31
2    42,1
3    48,6
4    53,2
5    56,8
6    59,7
7    62,1
8    64,3
9    66,2
10    67,8
11    69,4
12    70,8
13    72
14    73,2
15    74,3
16    75,4
17    76,3
18    77,2
19    78,1

How old is your pooch?