Lift the kitten’s tail gently
Look for the anus and the genital opening
Check the distance between the two openings
Identify a female by a short distance and a vertical slit below the anus
Identify a male by a larger distance and a round opening below the anus
Look for a pattern like an exclamation mark in females
Look for a pattern like a colon in males
Compare with another kitten if available
Check again when the kitten is a little older if sex is unclear
Ask a veterinarian if you are unsure