Abstract: A modular brassiere fitment apparatus may be provided for use in the determination of the brassiere size of a woman. The modular brassiere fitment apparatus has the same general appearance as an ordinary brassiere except that it is based on a modular system. The first module comprises a pair of breast cups, a connecting front panel, and two side panels. The second module comprises a back panel. A third module may comprise a pair of shoulder straps. At least two first modules and at least two second modules make up a modular brassiere sizing kit where each of the first modules has a different size and each of the second modules has a different size, one from the other. When one of the first modules is assembled to one of the second modules from the modular brassiere sizing kit, the combination of the first and second modules constitutes a modular brassiere fitment apparatus.