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Welcome to our weekly 'Ask a Vet from the SF SPCA' feature on They've enlisted their Co-President, Dr. Jennifer Scarlett, to answer your questions every week. Got a question for Dr. Scarlett? Ask away in the comments!

Q: My dog is turning four this September. How old is he in dog-years? Is the 7 year rule true?

A: Well, that's a more complicated question than it seems. The correlation between dog years and human years really depends on the breed and size. Some breeds tend to have longer lifespans than others. We checked around and found this chart on Wikipedia that illustrates a presumed correlation between size and age. We love graphs, so we will share it here, though can't say with any certainty that it is scientifically based.

While we can’t answer all of the questions here, please feel free to ask us during our Friday Twitter Ask the Vet Chat. If your animal’s problem is of an immediate nature, please call your vet or you can reach the SF SPCA at 415-554-3030 to make an appointment.