They all say do something different, and then there is vanity sizing. I just looked up how google says to measure, looked at three sites and literally found three different methods. I think if you go under the breast you are supposed to add inches to that measurement and the cup size it relative to that sum, but like you all say, some places don't say to do that. You just have to try them on and find your fit, and it isn't always easy even then.