I found this neat site that allows you to put in various information about your dog, from the food you feed, to Vaccinations, to activity levels and it computes your dog's ago in human years

Dog Age

How old are your dogs?

Sadie is 13.5, 5.8 years younger then others of her breed

Spot is 13.2, 5.7 years younger then others of his breed

Cincy is 13.0, 3 years younger then others of her breed