I think AgonyCat is right. My measurements are a bit higher than yours and I can wear 18's comfortably in most brands and some 16's in others. I plan on ordering some slacks through Land's End and am going to get the 16's. (I can pull the 20's off without unzipping or unbuttoning them). Even if they are a bit tight now, by the time I really want to wear them (October), they should fit me nicely.