The current popular system of determining bra size is inaccurate so often as to be useless. Add to this the many different styles of bras and the lack of standardization between brands, and one can see why finding a comfortable, well-fitting bra is more a matter of educated guesswork, trial, and error than of precise measurements. An improved method of determining cup size by directly measuring the circumference of the breast is presented in this paper. If adopted commercially, this simple method could reduce dramatically the number of women said to be wearing the "wrong-sized bra." The technique has also been found to be an accurate predictor of postoperative breast size in augmentation and reduction surgery, and thus offers plastic surgeons an opportunity to better meet the expectations of women undergoing these procedures.