"1. How to measure: First take a snug measurement under the bust line with a tape measure. Next take another measurement over
the fullest part of your chest. Again not too tight but not too loose. Take the average of theses two measurements and apply the result to the scale provided below. Each item has a different scale based on the elasticity of the fabric used and the cut of the garment, so please pay attention to the sizing scale for each style."
^that is taken from the underworks website
dont get something too small, some guys wear super tight too small binders, it really isnt healthy
