Understanding bra sizes can be confusing, especially when it comes to a 38 band size. The number “38” refers to the measurement around your ribcage, just below your bust. To determine your band size, measure snugly around your ribcage; if the measurement is an odd number, round up to the next even number to find your band size. The letter in a bra size represents the cup size, which corresponds to the difference between your bust measurement (around the fullest part) and your band measurement