The people who brought you Real Age now have an age calculator for your dog. I just took the quiz for Xena, my senior citizen at 12 1/2 years old. She's a retriever mix.
I have to say the test is a good 15 minutes long and very thorough. They get right down to the details of Fido's lifestyle, including whether or not he lives with a smoker. Wow! Apparently second hand smoke is not just a concern for our children.
Factors that came into the mix included weight, regular exercise, training, behavior issues, skin condition and much more. After a complete health history, you get an estimated age for your dog, and a 1 page report with their estimated age in human years.
I was pleasantly surprised to learn that Xena is a youthful 48.2. Given an approximate 7 years per human year, I expected her to be 84+. This was a big surprise and we celebrated with an extra scoop of organic dog food in her dinner bowl.
If you're interested in taking the test, either for yourself or your dog, here are the sites:
Real Age for humans
Real Age for dogs