Women often wear ill-fitting bras which cause pain, discomfort and sagging due to the over-simplified bra-sizing system used in the manufacture of commercial bras. In addition, a long development process is required for conventional bra design from creating the prototype to manufacturing the final product, which include the key steps of material selection, pattern making and grading. Thus, in order to reduce the time of the product development cycle and assist bra designers in determining individual bra fit that provides an optimal supportive shape and comfortable pressure, numerical simulation is a potential new tool. The objective of this study is to comprehensively provide information to bra designers so that they gain a better understanding of the interaction process between the breasts and bras with different design features by using numerical simulation. In order to achieve this objective, a study that involves three main stages is conducted: determining the realistic material coefficients of breast tissues to be used for building an accurate biomechanical FE model; developing a subject-specific FE model to simulate the wear process of a bra; and providing a parametric design for different bra features to evaluate the shaping effects of the breasts and pressure distribution on the body.