Wear a non-padded bra or no bra
Measure your band size around your ribcage, directly under your bust
Keep the measuring tape snug and level
Round the band measurement to the nearest whole number
Measure your bust size around the fullest part of your breasts
Keep the tape level and not too tight
Subtract the band size from the bust size
Use the difference to find your cup size
1 inch = A cup
2 inches = B cup
3 inches = C cup
4 inches = D cup
5 inches = DD or E cup
6 inches = DDD or F cup
Try on bras in the calculated size to confirm fit