Sizing is a FAQ around here so here's a chart to help you out!
Size Cup Size Ribs Bust
XS A < 27" < 31"
S B 28" - 30" 32"-34"
M C > 31" > 35"
We carry sizes XS / S / M and that loosely translates to A cup / B cup / C cup but it comes down to your fit + support preferences. Mediums accommodate some D + DD so make sure to check the support level of the product listing. If you're still uncertain or you fit in 2 size categories, include your measurements in your order notes and we'll make it custom fit!