Men's sizes are generally taken in terms of waist measurements. Meanwhile, women's clothing is generally less intuitive, with sizes ranging from 0 to 24 or larger. While there is no simple formula to convert all men's sizes to women's sizes, you can have a general idea of what to expect based on knowing your own measurements.
Subtract 21 inches from the waist measurement of pants to convert it into the women's pant size. The inseam measurement, usually the second measurement on a men's pant size, should remain the same, regardless of gender. For example, if you normally wear a 31 waist, you would wear a size 10 in women's pants.
Add 2 to the men's shoe size, which will convert the size to women's. If you wear a size 9 in men's, you will wear a size 11 in women's shoes.
Converting men's shirt sizes to women's sizes is somewhat trickier. Take measurements at the chest and waist of your men's shirt size, and compare the measurements to a women's size chart.