1. Stand in front of a mirror with a tape measure. Be sure to wear a bra that fits you well.
2. Pull the tape measure around your chest, just below your underarms. You want the tape measure to be firm against your body but not squeezing you. This measurement is your band size. If you get an odd number, round up.
3. Now, measure loosely around the fullest part of your bustline.
4. Your band measurement subtracted from your bust measurement will give you your cup size. Just find the correct number on this bra size chart.