Sizing Guide: Girls, Juniors, Women's Plus Clothing

I have been selling clothing for quite sometime now and almost always size is the #1 concern. You might wonder why you're a size 5 in Old Navy Jeans and a size 9 in Levi's. I know, it's quite confusing -- I don't even know my exact size as different stores and brand names vary in their sizing chart. Your best bet in buying the perfect fit? --- Your measurement.