- Have a seamstress' measuring tape handy. This will allow you to measure the circumference around your breast and rib cage with ease.
- Start with your rib cage measurement. Place the measuring tape directly below your bust where the underwire would normally rest. Make sure the tape is parallel to the floor and is completely level. When measuring, make sure the tape is nice and snug, similar to how a bra should fit. Record your measurement in inches.
- Once you have the measurement, add three inches. This is your band size. Bra manufacturers design bras with these measurements so don't worry about seeming bigger than you really are. An exception to this rule is if you measure over 40 inches. In this case, stay within an inch of your measurement. The larger your breasts, the snugger your band should be to support you.
- Once you have you rib cage measurement you'll need your cup size measurement. To find this, measure the fullest part of your bust. You should be wearing a non-padded bra for this part of the measuring. Padded bras will add volume to your bust and will subsequently confuse the measurement.
- Once you have both measurements, you'll be ready to learn your bra size!
- To find your bra size, you must subtract your rib cage measurement from your bust size measurement. (Note that your rib cage measurement is the number before you add the three inches.) For every inch difference there is a letter and that letter is your cup size.
1 inch = A cup
2 inches = B cup
3 inches = C cup
4 inches = D cup
5 inches = E cup (DD)
6 inches = F cup (DDD)
7 inches = G cup
- Take your band size and add it to your cup size. Viola! There is your bra size.
Example: Your rib cage measures 31 inches and your bust size measures 36 inches.
Your band size: 31 + 3 = 34. Your band size is 34.
Your cup size: 36 - 31 = 5 inches. 5 inches is an E cup (DD).
Your bra size = 34DD.
Things get a little more complicated if you're between sizes.
Example: Your rib cage measures 32 inches and your bust measures 36.5 inches.
Your band size: 32 + 3 = 35. Your band size is 35, which doesn't exist.
Your cup size: 36.5 - 32 = 4.5. 4.5 inches is between a D & E cup.
In this case, your bra size is between a 34E and a 36D.