虚荣尺寸（vanity sizing），也叫做尺寸膨胀，指随着时代的发展，各类成衣制品在尺寸号码不变的情况下，实际尺寸增大的现象。

　　The increasing dimension of garments of the same nominal size has caused some designers to introduce size 0, 00, or subzero sizes. Different manufacturers have modified sizes so that a woman who once wore a size 12 dress can now wear a 10 or an 8.

　　由于成衣实际尺寸的增大，不少设计师都开始引入“0号”、“00号”，甚至“负0号”尺寸。不同的成衣生产厂家也调整了各自的尺寸号码规则，原来穿12号衣服的女性现在能穿10号或者8号的衣服。

　　Many commentators have suggested that "vanity" sizing, as its name suggests, is designed to satisfy buyers' wishes to appear thin and feel better about themselves. While some others also suggests that vanity sizing allows clothing companies to cater their sizing to their demographic, since women of different sizes may be attracted to different brands. Finally, it has been suggested that vanity sizing merely reflects the increasing prevalence of obesity.

　　很多评论人士都表示，“虚荣尺寸”就是为了满足消费者想要看上去瘦一点儿的虚荣心理。不过，也有人表示，“虚荣尺寸”让成衣公司能够根据目标消费人群的特征来调整产品的尺寸，因为不同身材的女性可能钟情的品牌也不尽相同。总的来说，“虚荣尺寸”的出现说明肥胖人士增多了。