Wear an unpadded bra or no bra
Measure your band size by wrapping a measuring tape snugly around your ribcage, just under your bust
Round the band measurement to the nearest whole number
Measure your bust size by wrapping the tape around the fullest part of your breasts
Keep the tape level and not too tight
Round the bust measurement to the nearest whole number
Subtract the band size from the bust size
Use the difference to determine cup size
1 inch difference = A cup
2 inches difference = B cup
3 inches difference = C cup
4 inches difference = D cup
5 inches difference = DD or E cup
6 inches difference = DDD or F cup
Check both measurements again for accuracy
Try on bras in the calculated size to confirm fit