One year in a dog or cat’s life is roughly equivalent to 5-7 years of a human’s life. Large or giant breed dogs, in general, age faster and live shorter lives than smaller breeds. A 10 year old Labrador Retriever is roughly equivalent to a 70 year old human! We consider cats over the age of 10 and dogs over the age of 8 (giant breeds over the age of 6) to be seniors.