Wear a non-padded bra or no bra
Measure the band size around your ribcage, directly under your bust
Keep the tape snug and level
Round to the nearest whole number
If the number is even, add 4 inches
If the number is odd, add 5 inches
Measure the bust size around the fullest part of your breasts
Keep the tape level and not too tight
Round to the nearest whole number
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
Adjust for comfort, support, and fit
Recheck measurements regularly