How to calculate your dog's age in human years

How old is my dog in human years?

We've all been told that one human year is the same as seven dog years, but it turns out that's not actually true.

While no-one is really sure where that theory came from, it could have originated as far back as the 13th Century when monks wrote about it at Westminster Abbey in London!

In 1953, a French researcher published the theory that dogs age 15 to 20 times faster than humans do during their first year of life, but that ratio soon tapers off to about one dog year being the equivalent of five human years, but this is not always true for every breed or size of dog.


Now, there are various variations of that theory but to suggest all dogs age the same in an equivalent way to humans, just isn't correct. 

How to Calculate Dog Years to Human Years

However, there are certain clues to guaging how old your dog is in human years. As a rule, the American Veterinary Medical Association breaks it down very simply like this:

  • 15 human years equals the first year of a medium-sized dog’s life.

  • Year two for a dog equals roughly nine years for a human.

  • After that, each human year is approximately five years for a dog.

Average life expectancy of a dog

Small dogs live longer than bigger dogs but male and female dogs have similar life expectancies.

Small dogs (less than 17kg) are expected to live for between 13-16 years.

Common breeds: Maltese, Dachshund, Miniature Poodle, Pomeranian

Medium sized dogs (11-17kg) live to between 11 and 14 years.

Common breeds: American Staffordshire Terriers, Cavalier King Charles, Beagles

Large dogs (18-31kg) live to nine to 12 years of age.

Common breeds: Boxers, Cocker Spaniels, Australian Shepherds, Bull Terriers

Extra-large dogs (32-40kg) lifespan is around eight to 10 years.

Common breeds: Golden Retriever, Labradors, German Shepherds, Rottweilers

Extra-Extra-Large Dogs (40kg+) are expected to live for between six and eights years.

Common breeds: Great Danes, Bernese Mountain Dogs, Newfoundland,

For a breed specific age calculator, click here.

Cross breed dogs or mutts have a longer lifespan than pedigree dogs as generally speaking they have the least number of health problems.

Signs of ageing

Technically speaking a dog is considered “old” when they have reached three quarters of their life expectancy but there are also a couple of signs to look out for:

  • Gray hair, starting at their face then the rest of the body
  • Stiff legs
  • Poor hearing
  • Worn or missing teeth
  • Decaying vision and white cataracts

What is the longest living dog breed?

The Yorkshire Terrier is one of the longest living dog breeds with an average life expectancy of between 17-20 years.

What is the record for the oldest dog ever?

The Guiness World Record for the oldest dog is an Australian cattle-dog named Bluey who lived to the age of 29 years and 5 months old.

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