Band Size and Ribcage Shape
Let's start with the band. When we measure around our ribcage (the parallel line directly below your breast root) it tells us the circumference of only part of our ribcage. Bra bands are several inches deep and wrap around a greater depth than the single ribcage measurement we can take with a measuring tape. I want to make it clear that the underbust measurement is well worth taking because it's a great starting point but for lots of women it needs to be taken in conjunction with other bra fit factors.
If you have a broad back or a flared ribcage (it's worth reading my article on torso shape and bra fit) then your band has to stretch around large and small circumferences simultaneously. The measuring tape measurement probably tells you the smallest circumference that your bra band will stretch around which is why someone like Cora can measure a 30 around but find her best fit in a 34 band because her ribcage might flare out into a broader back or acute angle which is better suited to a larger band.
|Cora, The Lingerie Addict, in a shoot by Old School Pinups wearing Kiss Me Deadly Sirena Corset|
Breast Bone Shape
The other fit factor to consider when a larger band fits you better than a smaller one is the angle and shape of your breast bone. When you measure around your ribcage it cannot take into account the shape of your breast bone (sternum). When your sternum is acutely angled or protruding you often find that you need either a very short gore than sits below your sternum or you need a larger band to accommodate the shape of the breast bone. You may find that your breast bone hollows where your gore is meant to tack, or that it protrudes more at the top than the bottom. This shaping of your sternum affects which band size and gore height will work best for you.
The band number and cup letters are far less important than finding a fit that feels right to you so don't worry if you measure a 28GG but find that a 30G or 32FF fits you better, it could very well be that other aspects of your torso are affecting your fit. xx