Males tend to be 8-10 inches long and females tend to be 7-8 inches long. But, if they are still young it's hard to tell for sure. It is best to wait till their about 6 months old. A different way to determine their gender is that male leopard geckos have a distinct V-shaped row of pre-anal pores in front of their cloaca. As a gecko matures, these round pores that look like dots become quite prominent and exude a waxy material. Females have a similar row of small pores, but they are not nearly as obvious. Female pre-anal pores are barely noticeable and they do not exude the waxy substance that male leopard geckos do.