I don't measure my ribbon before I do the bow (I do the bow and then cut the ribbon
) but, they come out around 2 1/2 inches wide by 2-2 1/2 inches long depending on how long I make the tails. I have a pretty good eye for those, so I don't measure them before hand. This is with the 5/8" ribbon.
I just made a big one of 7/8" ribbon to match a dress my dd has because there is a bow on her dress that is that style. I made that bigger and it is almost 4" wide and 4 1/2 inches long. I made it a lot bigger because I then used 3/8" ribbon in the center to make it a double layer.