Wear your best fitting, unpadded underwire bra. Measure one breast, beginning at the breast bone, and starting from the outer edge of the under wire, across the fullest part of the breast (across the nipple area), to the outer edge of the under wire on the other side near the underarm. This measurement is your Cup Size. Note: If you measure in a minimizer, add one inch to the measurement, and if one breast in larger than the other, use the larger size.