The average life span of the North American or European dog is 12.8 years. This is a large increase in life span over the past 100 years and is mostly attributable to better food and better medical care. Within this 12.8 year average for all dogs is a large range of life spans where certain breeds live longer and certain breeds live less long. In general, larger dogs live shorter lives than smaller dogs. This is due to the fact that the bodies of larger dogs must work harder (are more stressed) than the bodies of smaller dogs. That said, the life expectancy of any one dog in particular is ALSO determined by the stresses in its life (both physical and psychological), what it eats and how well it is taken care of.