While you can totally do this at home, it’s a blast to visit a lingerie store with a real fitter. They use the same math, but with extra wizardry.
Most people end up in a band size smaller and a cup size larger than they expected. If a fitter hands you a 30E, don’t panic—just try it on. It might feel like a cloud.
At the end of the day, a correct bra size isn’t about a number on a tag. It’s about freedom. Freedom from discomfort, from tugging, from thinking bras just “suck.” They don’t suck. You were just wearing the wrong math.