If you wear a size 6 shoe in mens sneakers then what size are you if you wear a womans size sneaker?

As I understand it, women's shoe sizes are generally 2 full sizes higher "numerically" than men's, so a women's 6 is a men's 4 , but since I've never seen a men's size 4 you're probably looking at having to get boys sizes and I'm unsure about the conversion.