A DD cup size in cm measures 10.16 cm (4 inches) larger in circumference than an AA cup on the same band size. This measurement represents the additional volume needed to accommodate a DD cup compared to an AA cup.
Cup sizes are relative to band sizes. A DD cup on a 32-inch band is smaller in absolute volume than a DD cup on a 36-inch band because the cups scale proportionally with the ribcage.
The difference between cup sizes is consistent: each letter increase (, B to C, etc.) adds approximately 1.27 cm (0.5 inches) to the bust circumference at the fullest point. Therefore, a DD cup is 7.62 cm (3 inches) larger than an A cup on the same band size.
Cup sizes follow an alphabetical scale starting at A, with some variations:
| Cup Size | Additional Circumference vs. AA (cm) |
|---|---|
| AA | 0 |
| A | 1.27 |
| B | 2.54 |
| C | 3.81 |
| D | 5.08 |
| DD/E | 6.35 |
| DDD/F | 7.62 |
Some brands use D, DD, DDD while others use D, E, F. Both systems represent the same cup volumes.
Cup sizes are not absolute measurements but represent the difference between bust circumference and band size. For example, a 34DD bra has a band measuring 34 inches and cups that provide 10.16 cm (4 inches) more coverage than an AA cup on the same band.
This relative sizing helps bras fit proportionally to different body types. A DD cup on a smaller band size will have less volume than a DD cup on a larger band size, even though the letter designation is the same.
Many people confuse cup size with bra size. A DD cup does not indicate a larger bra -it only specifies the relationship between bust size and band size. Two people can both wear a DD cup but have different band sizes, resulting in different bra sizes.
Another misconception is that cup sizes are fixed measurements. In reality, they scale with band size. A DD cup on a 32-band is smaller in volume than a DD cup on a 36-band, even though both are labeled DD.
For a practical example, consider two individuals: one with a 32-inch band and 38-inch bust, and another with a 36-inch band and 44-inch bust. Both would wear a DD cup size, but their bras would differ in size due to the varying band measurements.