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1 Human Year Equals Seven Dog Years? Think Again.

How old is your dog really in human years?

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Header photo: Eric Isselee/

Most dog people are familiar with the stock-standard formula ‘one dog year equals seven human years.’ The problem is this equation was never based on strong scientific research. It most likely resulted from a comparison of the average lifespan of a dog (around ten years) and the average lifespan of a human (around 70 years) and fails take into account differences in the maturation arc. 

In a study undertaken by Trey Ideker and colleagues of the University of California, San Diego, new in-depth research debunks the ‘one dog year equals seven human years’ equation, concluding that dog and human aging is significantly different and that the relationship between human and dog age is nonlinear. 

The researchers show that dogs develop rapidly in their youth but that the aging process slows significantly as they age. The data suggests a one-year-old dog is actually equivalent to a 31-year-old—not a seven-year-old—human, while a two-year-old dog is equivalent to a 42-year-old human and a three-year-old dog is  equivalent to a 48-year-old human, with the researchers seeing a smaller and smaller increase in the human-age equivalency of the dogs as the dogs age. 

Using DNA collected from 104 Labrador Retrievers up to the age of 16, researchers compared changes in the dogs’ DNA to the DNA of 320 humans, aged 1 to 103. By looking at similarities, they found that dog and human DNA profiles could be matched at certain ages. For example, they found similarities between a two-year-old dog’s DNA and a 40-year-old human’s DNA, suggesting an age equivalency. These matches became the basis for their new formula to equate dog years to human years.

To calculate your own dog’s age in human years, simply insert this formula into a scientific calculator or online logarithm calculator:

16 ln (dog's age) + 31 = dog's age in human years

It turns out that your three year old pup, who you’d thought was similar to a youthful 20 year old, could actually be pushing 50!

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