Every woman who wears underwire bras needs to understand underwire sizing. Breasts have a diameter and a projection. When you select
a cup size (e.g. B, DD etc.) you are making a breast projection selection.
Each band size has a pre-determined breast diameter built into it in the form of an underwire. Changing your band size can
change the underwire diameter. It is also a fact that the same size underwire is used in different cup sizes - the underwire
in a 36C is the same underwire used in a 34D and a 38B cup sizes.
Finding Your Underwire Size:
Find your bra size on the chart below. Every bra size in the same diagonal color stripe uses the exact same underwire size.
Now that you understand underwire sizing, here's how you can use this information. Say you've found a bra that fits you great
in the cups, but is tight around your ribcage. You now know that when you go up a band size and down a cup size, you will have
the same fitting cup diameter (the same wire will be used) but a larger band. This also explains why underwire swimsuits with
just a cup size like a "C" don't fit all C cup women. And, for you analytical types who are probably wondering, the diameter
increase between standard underwire sizes is approximately 3/8". A standard underwire's length increase between sizes is
designed to have some spring. Made out of heavy gauge wire, sheet metal
or plastic, they splay or spread wider once a bra is put on and fastened.
Then they return to their original shape when the bra is taken off. This
springing or splay gives additional support to your breasts. If your breasts
are wider than the splayed diameter of the underwire, over time the pressure
and weight of your breasts can cause an underwire to break in half. Wire
breakage can also occur if your band size is too small and thus over-splaying
Underwire shapes can vary among brands. In fact, lingerie manufacturers claim their underwire grading and shaping to be the secret behind their unique
fit. This is why you may find wire variations among manufacturers. This is also why one manufacturer may fit you better than another. Underwires also have
different lengths - though their curve will maintain the same shape. For example, demi cup and low-plunge bra styles will have shorter wires. Underwires in
petite bras will also be shorter in length to accommodate a shorter torso. Strapless bras tend to have the longest underwires. Since they do not have the
benefit of strap support, strapless bras compensate by having more wire surrounding the breast to give more support.