The old cliché is that every year of a dog's life is equivalent to seven human years. In other words, a five-year-old dog is like a 35-year-old human. But it's not so simple. The rate at which dogs develop is different than for humans, and the dog's size and breed make a big difference to its lifespan.
Humans take 18 years to reach adulthood, but puppies are only pups for six to nine months (depending