Red-eared sliders are generally like other animals, difficult to tell if it's a male or female until they reach maturity. Once they do, the males generally have longer claws than the female, and in some cases more defined red markings on their head. Hope this helps.
Also the way I figured out if mine was a boy or a girl was to go online. The markings on the bottom of there shell can determine that, also the length of their tails. Hope this helped
