Pet dogs are increasingly treated like “little humans. Just as we tend to categorise ourselves by our age, so we often like to compare our pets to their human age equivalent. There’s a logical way of approaching this, and it starts by ignoring the method that most people have heard of...

1. Forget the old myth that one human year equals seven dog years

This is the traditional method of calculating a dog’s “human” age. It makes the assumption that since dogs have shorter lives, their life flashes past at a rate that’s simply speeded up on a pro rata basis compared to our own. So given that the average human life expectancy is around eighty, and an average dog might live for eleven years or so, this works out at around seven dog years equalling one human year.

While this comparison has been in use for fifty years or more, and it may be broadly correct for an “average” older dog, there are aspects which are plainly wrong.