Downsize your assumptions: men think an 18cm erection is perfect, but women actually prefer about 3cm less, a study in the journal Psychology of Men & Masculinity reveals. Not only did women not consider a larger-than-average penis desirable, but their ideal size matched that of the average package. “The mythology of the oversize penis comes from men’s desires, not women’s.

It’s a way men size each other up,” says sex therapist Brandy Engler. In fact, a giant erection can be uncomfortable for some women, Engler says.