QUESTION ON UGG BOOTS?

I want a new pair of Uggs that I am ordering online, but unfortunately I don't understand the sizing. On the tag of my current Uggs it says SIZE W 5. Now to me that means Wide 5, but I know for a fact that i'm not a size 5 since I normally wear a 6-7 shoe and I didn't think that they came in wide. I was just wondering if anyone could help me out with what size this is.