Step 1: Rib Band Measurement
Measure your chest above your breasts - make sure the tape is around your back and under your armpits. Check in the mirror to ensure the measuring tape is parallel to the floor along your back. The tape should be snug around your body without any fingers underneath the tape. If you are in between band sizes, round up or down to the nearest even number. This will be your rib band size (34, 36 etc.).
Step 2: Cup Size Measurement
Measure around the fullest part of your breasts, over your nipple area. This is a looser measurement than the rib band measurement. While holding both ends of the tape with one hand at the side of your breast, use your free hand to press the measuring tape in between your breasts to your chest. This will provide a more accurate cup size.
Step 3: Do The Math
Subtract the rib band measurement from the cup size measurement. The difference represents your letter cup size (1=A, 2=B, 3=C, 4=D). Cup size chart: