Measure your band size by wrapping a tape measure 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 measure around the fullest part of your breasts
Subtract the band measurement from the bust measurement
Use the difference to determine the 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
7 inches difference = G cup
Combine the band size and cup size to get your bra size
Example: 34 band and 37 bust = 34C