Statistics have shown that quite a number of women are wearing the wrong cup and/ or band size.
Wearing an improperly-sized bra will offer poor back support and increase back pain. In addition, the weighed-down effect will trickle into a hunched-over stance and dig into your shoulders. In the long run, your posture will suffer .
Conversely, the right fit will give the illusion of a trimmer waistline and ultimately, make you feel more comfortable.
Before we go any further, consider the following questions: 
-Do the bras you wear leave red imprints?
- Do you feel a load of relief after removal? 
-Is removing your bra the best part of your day? Yes? Then let’s proceed.
Band size: Use a tape measure to go around the part of your rib cage right under your bust. Add between three and four inches to that value. Keep in mind the band will stretch after a few uses, so you don’t want to start off with a size that’s semi-loose on the last notch.
Cup size: Circle the tape measure around the fullest part of your bust so that it is snug but comfortable. Round it to the nearest even number and subtract it from the band size value. 1 = A, 2 = B, 3 = C, 4 = D and so on.