This paper analyzes how to measure breast volume and the change in breast volume after wearing a brassiere. Measurement using a breast replica is used to measure the breast volume of 41 women in their twenties. The rate of persons having flat and hemispherical breast are high. The majority of subjects are size 75A, 80A, and 75B, and their under-bust size is 70. The current size specification should be refined for fitting according as the girth under bust decreases. The correlation between breast volume and the circumference of the breasts was high. It was more reliable to set up the cup size of a brassiere using the breast circumference. The mean breast volume is 263.68cc (nude) and the total volume wearing brassiere is 342.05cc. The volume difference according to wearing a brassiere is 78.37cc, which is less than the brassiere volume itself. The results show, the less breast volume of a subject, then the greater volume in wearing a brassiere.