The amount of weight in a size is very dependent on a number of factors . . . (not to mention the clothing manufacturer and how slavish it is to 'vanity sizing') . . . two of the main ones, of course are your height and your basic body 'type'.
One thing that I find is more consistent is that the difference in inches for a size (women's sizing at the hips is what I go by) is generally 2 inches. (For men's sizing probably 2 inches at the waist.)
Just be patient, it will happen. Hope that helps a bit.