Are ‘Dog Years’ a myth?

DrPaul -

Are ‘Dog Years’ a myth?

It has been a commonly accepted “rule of paw” that one human year is equivalent to seven dog years, but recent evidence suggests that dogs are ageing much faster than this and that ‘human age’ is in fact closely linked to the size of your dog.


For example, if the age old saying of “1 dog year to 7 human years” were true then a nine-month-old dog that can technically start having puppies could be the equivalent of an almost 7-year-old human child, which definitely doesn’t make biological maths!


So, what is the latest research and how do our dogs age when compared to their owners?


According to the American Veterinary Medical Association, the latest formula for calculating how old your dog is in human years should be broken down into years 1, 2 and then each year thereafter. 


A medium sized dog, such as a spaniel would age:


  • 15 human years to the first year of a medium-sized dog’s life.
  • Year two for this dog would equate to about 9 years for a human.
  • Each year after that would then be the equivalent of approximately 5 human years.


It is important to be aware that different breeds of dog do age differently with larger dogs ageing at a much more accelerated rate when compared to their smaller counterparts, meaning smaller breeds do generally live for longer.


For those larger and giant breeds the formula for calculating their human age is slightly different as these dogs age faster in human years as they get older. A 10-year-old spaniel would be around 60 human years, but a 10-year-old mastiff would be getting on for an 80 year old person! Quite a stark difference!


But why is this? Why do smaller dogs live longer and age more slowly when compared to larger ones? Usually, large mammals such as elephants or whales usually live longer than smaller mammals, but dogs seem to completely defy the norm and so, as it stands, this question remains largely unanswered. According to researcher Cornelia Kraus, an evolutionary biologist at the University of Göttingen in Germany, large dogs age at an accelerated pace, and “their lives seem to unwind in fast motion”.


Regardless of how our dogs age, I think we can safely say that they don’t live long enough which makes their time with us all the more important.

Paul Manktelow

Veterinary Surgeon

Dr Paul Manktelow is a vet who's worked for almost 20 years on the front line in some of the UK's busiest veterinary hospitals. Paul also appears regularly in the media as a TV and radio presenter, writer, public speaker and podcast producer.