'Dog Years' Just Don't Add Up

A human year is 7 dog years, right? That ubiquitous formula has been driving veterinarians and dog enthusiasts nuts for decades. If it were accurate, some pooches would live to the equivalent of age 150 or so, Carl Bialik writes in the Wall Street Journal. For those who must convert, he suggests scrapping the one-size-fits-all approach in favor of a more nuanced formula.

The truth is that there is no hard and fast age equivalency: Veterinary researchers have found that dogs grow 20 times as fast as humans before age 1, then slow down. Dog lifespans also vary from breed to breed, and all dogs have benefited from improvements in veterinary care in recent decades. So is the end near for the 7:1 formula? Nope. "You can't really kill the 7-year rule," said one expert. (More dog stories.)