Look at the distance between the anus and the genital opening
Male kittens usually have a larger gap between the openings
Female kittens usually have a smaller gap between the openings
Male kittens often have a round genital opening
Female kittens often have a vertical slit-shaped genital opening
Male cats may have visible testicles after a few weeks of age
Female cats do not have testicles
Male cats often have a more rounded, broader head
Male cats are often larger and more muscular
Female cats are often smaller and more slender
Check with a veterinarian if you are unsure