You can tell if a leopard gecko is male or female by looking at the underside of the body, just in front of and behind the vent (the opening at the base of the tail). Males have two distinct features that females lack: a V-shaped row of visible pores between the back legs and two oval bulges just past the vent. These traits become reliably visible once a gecko reaches 35 to 40 grams in body weight, typically around 18 to 24 months of age.
When You Can Reliably Sex a Leopard Gecko
Trying to sex a juvenile leopard gecko is mostly guesswork. The physical differences between males and females don’t develop until the gecko approaches sexual maturity, which happens at roughly 35 to 40 grams of body weight. For most geckos, that means somewhere between 18 and 24 months old. Before that point, the pores and bulges that distinguish males simply haven’t developed enough to see clearly.
If you recently bought a young gecko and want to know its sex, a small kitchen scale is your best friend. Weigh your gecko periodically. Once it’s consistently in the 35-gram range or above, flip it over gently and check for the markers described below.
Pre-Anal Pores: The Easiest Marker
The most reliable way to sex a leopard gecko is to look at the underside, right where the back legs meet the body. Males have a distinct row of small dots arranged in a V-shape that runs across the thighs and angles down toward the vent. These are pre-anal pores, and on an adult male they’re easy to spot with the naked eye. They look like a line of tiny, slightly raised pinpoints.
These pores secrete a waxy material made of keratin (the same protein in your fingernails) or a fatty, lipid-based substance. In the wild, this secretion rubs off naturally as the gecko walks across rough surfaces like rocks and branches. In captivity, you might occasionally notice a yellowish, waxy buildup in these pores, which is completely normal for a healthy male.
Females technically have pre-anal pores too, but they’re so tiny they’re nearly invisible. If you’re looking at your gecko’s underside and you have to squint or debate whether you see pores at all, you’re likely looking at a female.
Hemipenal Bulges: The Confirmation
The second feature to check sits just behind the vent, right at the base of the tail. Males have two small, oval-shaped bulges on the underside of the tail, one on each side. These bulges house the hemipenes, the paired reproductive organs found in male lizards. On an adult male, they create a noticeable widening at the tail base that’s easy to see from below.
Females have a smooth, flat profile in this same area. The tail base tapers without any visible swelling. If you’re checking both markers together, a gecko with clearly visible pores AND two distinct bulges behind the vent is almost certainly male. A gecko with neither feature is female.
Body Size Differences in Adults
Once fully grown, males and females differ noticeably in overall size, though this alone isn’t a reliable sexing method. Adult males typically reach 20 to 28 centimeters (about 8 to 11 inches) in total length and weigh 60 to 80 grams. Adult females are smaller, usually 18 to 20 centimeters (7 to 8 inches) long and 50 to 70 grams. Males also tend to have wider, blockier heads and thicker necks compared to females of the same age.
These size differences overlap enough that you can’t sex a gecko on body size alone. A large female and a smaller male can look quite similar. But if you’ve already checked the pores and bulges and want additional confirmation, overall build can support your conclusion.
How to Check Safely
To inspect your gecko’s underside, let it walk onto your hand voluntarily rather than grabbing it from above. Once it’s comfortable, gently cup it in your palm and slowly tilt your hand so you can see the belly. You can also let the gecko walk across a clear glass surface (like a clean baking dish) and look from underneath.
Never grab a leopard gecko by the tail. Like many lizards, they can drop their tails as a stress response, and while it does grow back, the regenerated tail looks different and the process is stressful for the animal. Keep handling sessions brief, especially if the gecko seems agitated.
Temperature Determines Sex Before Hatching
Leopard geckos are one of the species where incubation temperature controls whether an embryo develops as male or female. This is called temperature-dependent sex determination, and it means that breeders can influence the sex ratio of a clutch by choosing specific incubation temperatures.
Research published in PubMed shows the ranges clearly. Eggs incubated at 26°C (about 79°F) produce 100% females. At 30°C (86°F), roughly 70% are female. The sweet spot for males is 32.5°C (about 90.5°F), which produces approximately 75% males. Interestingly, pushing the temperature higher to 34°C (93°F) swings back toward females, producing about 95% female hatchlings. There’s no single temperature that guarantees 100% males.
This is why breeders who sell “guaranteed male” or “guaranteed female” hatchlings based on incubation temperature alone are making a strong bet, not a promise. The only way to know for sure is to wait until the gecko matures and check the physical markers.