The 1st pair I bought was medium. I’m 5.2 and 128lbs. They fit good and comfortable. The material is stretchy and lightweight. I like them so much I now own all together 4 pairs. However, I bought the later in small and they fit perfect. I think the size of this style is forgiving, because the pants are baggy. As for washing, you just throw it in the washing machine and dryer, no problem at all. So don’t hesitate to get one or several, they are quite comfortable.