Wear an unpadded bra or no bra
Measure snugly around your ribcage directly under your bust
Round the underbust measurement to the nearest whole number
Measure around the fullest part of your bust
Round the bust measurement to the nearest whole number
Subtract the underbust 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
Combine the band size and cup size
Example: 34 underbust and 37 bust = 34C
Try on the size and adjust if the band feels too tight or loose
Check that the cups fully contain your breasts without spilling or gaping