1. Measuring Your Band Size
Holding the measuring tape gently but firmly, measure around your bra directly under your bust after expelling all air from your lungs - you want this measurement to be as small as possible. Look in a mirror to assure the tape is parallel to the floor. The position of your tape measure is critical here. If you have the tape too high, your measurement will be too large; too low and it's too small. Pay close attention to make sure your tape is level and in the right location. Note: When you take these measurements, round to the closest whole inch, either up or down. (For example, if your measurement is 29 3/8", round to 29". If your measurement is 29 1/2" or more, round to 30".)
Bras come in even band sizes. If the rounded measurement you come up with is an even number, add 4 inches. If the rounded measurement you come up with is an odd number, add 5 inches. The result is your band size.
Example: 33" + 5" = 38" band size
2. Measuring Your Cup Size
Standing straight, with your arms at your side, measure around your body at the fullest part of your bust (while wearing a bra with your bust apex being midway between your elbow and your shoulder). Wrap the tape measure around you so that it is just touching, but not binding. If one of your breasts is significantly larger, put some type of padding in the cup of the smaller breast to make it even with the larger breast before taking your measurement. Note: Again, look in a mirror to assure the tape is parallel to the floor. Round up or down to the nearest inch as you did to find your band size.
Now, subtract your band size measurement from this second measurement. The difference is your cup size.
Example: 38" - 34" (band size) = 4" = D cup size