Wrap the tape loosely around the fullest part of your chest. Don’t pull it tight—just ensure it’s level all the way around.
Numbers are just a starting point; the mirror tells the truth. Look for these signs of a good fit: how to buy correct bra size
It should be level all the way around. If it arches up your back, the band is too big. You should be able to fit two fingers underneath it. Wrap the tape loosely around the fullest part of your chest