BLu Crochet Swimwear Sizing How To Measure Bust – Measure under your bust and straight to the center of the areola. Under Bust – Measure across the fullest area of your bust and straight around the back to determine cup size. Waist – Measure halfway between your lowest rib and the top of your hip bone.Hip: To measure your hips, place the tape measure around the fullest part of your buttocks. NOTE: Most of our designs are with straps for better adjustment.