Most women have never been properly measured, and most are wearing a size that is close but not quite right. That is not a criticism — sizing across brands is inconsistent enough that even a correct size in one label can be wrong in another. Here is what the numbers actually mean.
Band size
The band is the number — 32, 34, 36 and so on — and it measures directly under the bust, where the band of a bra actually sits. It should feel snug but not tight, and it should sit level all the way around, not ride up at the back. If you can pull the back of the band away from your body by more than an inch or two, the band is too big.
Cup size
The letter — A, B, C, D and beyond — is not a fixed size. It is a relationship: the difference between your bust measurement and your band measurement. That is why a D cup on a 32 band looks and fits completely differently to a D cup on a 38 band. The letter alone tells you nothing without the number next to it.
Sister sizing
If a 34B feels tight in the cup but the band is right, a 32C will often have the same cup volume with a slightly smaller band. If the cup is right but the band feels loose, a 36A may fit the same volume better. This is called sister sizing, and it is the fastest way to fine-tune a fit that is almost, but not quite, correct.
Signs your size is wrong
- Underwire that sits on breast tissue rather than around it
- Straps that dig in or constantly slip
- A band that rides up at the back
- Gaping at the top of the cup, or spilling over the top
When in doubt
Sizing charts are a starting point, not a guarantee, because every brand cuts slightly differently. If you are between sizes or unsure, the fastest route is simply to send us your underbust, bust, waist and hip measurements — we would rather help you get it right the first time than have you guess.