Bra sizing is bonkers. Really. We often say that there are three layers to the madness: the first is that, like other garments, there isn't enough sizing consistency across brands and styles to really rely on the label. (Solution: try everything on before you buy it. See here for a great article about why focusing the bra fit conversation on size is sort of missing the point.) Secondly, different parts of the world apply different letter names to their cup sizes. Lastly, and most misunderstood, those letters don't mean anything at all by themselves!
It's true... Whether talking about B cups, D cups, or any other size, the volume of those cups varies with the band measurement. The cups on a 32C and a 42C are completely different! This is because each sequential cup size represents one inch of difference between the under-bust measurement and the widest circumference of the bust. When you go up or down in band sizes, you have to adjust cup sizes also or the volume changes.
If all of this sounds like a giant headache, we're more than happy to help you navigate, and if you've always worn small cups, (especially if you have a relatively petite frame,) you might be very surprised to learn that your optimal cup size is bigger than you think!
You may notice that we sometimes specify US/UK/European sizes when discussing bra cups. This is because different parts of the world call their sizes by different letter names. All these systems agree on A through D cups, then diverge. US sizing uses the familiar DD/DDD/DDDD or G, then proceeds through the alphabet. UK sizing duplicates more letters and omits others: DD, E, F, FF, G, GG, H, HH, J, JJ, K, etc. Possibly the most straightforward, European sizes take us straight through the alphabet with no duplications. The extra "doubles" mean that UK sizes appear to climb more slowly than US or European sizes, but a UK F or G is actually a larger size.
Grail refers to our bra sizes according to what our various brands call them, rather than reducing all sizing on the floor to one generic system. We carry bras covering a size range from A-cups through UK K or US O-cups!
You don't need to remember all of this to shop with us, though; we'll do the conversions for you!