What is a bra cup?
The cup is the part of the bra that covers and supports the breast. The letter associated with each bra size refers to the cup's depth.
How do you know if you're wearing the right bra size?
The cup should perfectly hug the shape of the breast. If the breast spills out of the cup, you should try a larger cup size (e.g., a D instead of a C). If, on the contrary, there are gaps and empty spaces to fill, you should try a smaller cup size.
How can you be sure your bra fits properly?
The bra's straps shouldn't slide off your shoulders or dig into your skin. Additionally, the bra band shouldn't ride up in the back. If this happens, tighten the bra by using the next set of hooks or try a smaller band size (e.g., 34 instead of 36).