Eight in ten people consider their dog a member of their family. So, it is not surprising that43 percent of dog owners celebrate birthdays, according to a study done by Purina Pet Institute. The celebration includes a new toy, or a special trip to the park. But a doubt will emerge if, for instance, I try to calculate how old is my dog in human years. 

Once upon a time, it was an easy task to translate the age of a dog into human years. All you had to do was multiply the age of the dog by seven. But now it seems that it’s not so simple. If Sparky is ten years old, he’s not necessarily as old as a seventy year old human. Think about this: If it were truth that one dog year is like seven human years, a dog at the age of one would be like a human at the age of seven. But a human can’t reproduce at the age of seven, while a dog can reproduce at the age of one.

A two month puppy is approximately like a 14 month baby; a 6 month puppy is like a 5 year old kid; an 8 month puppy is like a 20 year old human; a dog at the age of three is like a person at the age of thirty; a five year old dog is like a forty year old person; and a dog who’s seven years old is like a human who is forty six. What is more, according to the BBC, not every breed ages in the same way. Besides, dogs may age at different rhythm at the different stages of their lives. And size is fundamental to determine how old the dog really is.

Ezequiel Olivieri y Julieta Balduzi, directors of a website devoted to pets, explained, “Statistically, the bigger the dog, the less they live. The biggest ones have a life expectancy of 12 years and the smallest ones can live up to 16 years or more. This depends, of course, of the quality of the food, the hygiene and the life style”. They then added, “It’s fundamental to take into account that a dog reaches its definitive size in its first year, that’s when we can evaluate its size”.

A source from the BBC explained, “If you think in the statistical correlation between the life expectancy and body size in mammals, generally, it tends to be positive: Gorillas, elephants and wales live much longer than hamsters and mice”. Therefore, a Rottweiler should live longer than a Yorkshire. But it’s actually the other way around. This is because small dogs have a shorter youth and a longer adulthood. They grow faster during their first 24 months, but their growing slows down as they mature. As strange as it might seem, a small dog at the age of two is older than a big one of the same age; but the small dog will be younger than the big one when they are both 5.