Lift the kitten’s tail gently
Look for the distance between the anus and genital opening
A female kitten usually has a vertical slit close to the anus
A male kitten usually has a round opening farther from the anus
Male kittens may have a slight bulge between the openings
Compare with another kitten if possible
Check again when the kitten is a little older if unsure
Ask a veterinarian to confirm