Visit a sports label store and get measured for a sports bra instead of wearing the wrong one. An adjustable sports bra will help you adjust your fit and therefore, it is best to invest in one. The band of the sports bra provides the majority of its support. Measure the area below your bust around your rib cage to determine the appropriate band size. Round the measurement up to the next even number if it is odd. Your band size is represented by this rounded-up figure.