A size 11 in U.S. women's shoes is the same as a men's size 9, according to About.com. This is based on a size chart that most companies use to create unified products for their customers.
The easiest way to convert men's to women's shoe sizes is to subtract two sizes from the women's shoes. This conversion works for most types of shoes, such as boots, sandals and dress shoes. In some cases, sneakers or tennis shoes have a slightly different conversion, which means subtracting only one and a half shoes sizes instead of two, so a women's 9 shoe becomes a men's 7.5 instead of a size 7.