Wear a non-padded bra or no bra
Measure your band size around your ribcage, directly under your bust
Keep the tape level and snug, but not tight
Round the measurement to the nearest whole number
Measure your bust size around the fullest part of your breasts
Keep the tape level and relaxed, not compressing the breasts
Subtract the band measurement from the bust measurement
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
7 inches = G cup
8 inches = H cup
Check the brand’s size chart, since sizing can vary
Try on a few sister sizes if the fit is close but not perfect
Make sure the center gore lies flat
Make sure the band stays level around your body
Make sure the cups fully contain your breasts without spilling or gaping