If you've just picked out the purrfect kitty companion for your household and are mulling over cute cat names, you'll want to know how to sex your kitten. The hardest part of determining whether your kitten is a boy or a girl is keeping the feisty little fluff-ball still long enough to check.
When to Look
Though it isn't difficult to determine the sex of a kitten, you'll need to wait until your kitten is at least a month old to check. The mother cat recognizes her newborns by smell; when humans handle a kitten too soon after birth, the kitten's mother may fail to recognize the kitten as hers and may push it away and refuse to feed it.
Around week 4 after birth, kittens begin to explore and their mother begins to leave them alone for short periods of time. It is possible to differentiate between a male and a female at 4 weeks, but it is much easier after about 10 to 12 weeks, when a male kitten's scrotal sac, the skin pouch holding the developing testicles, begins to bulge as the testicles develop, making it more clearly visible.
Male Kitten Parts
Hold the kitten in one hand and use your other hand to gently lift the tail. On a male kitten, the distance between the anus and penis will be roughly a half inch or so. Between the anus and penis, a male kitten will have a scrotum -- the sac covering his developing testicles. A very young male kitten may not have a visible scrotal sac. If a large space exists between the anus and genitalia, check for testicles by placing two fingers on opposite sides of the space where the scrotum would be and gently pinching the skin together. If the kitten is male, you should feel two small, smooth, side-by-side objects under the skin.
Never push on a kitten's penis, as it can be easily damaged. A male cat's penis will not protrude on its own until he is around 6 months old. A male kitten's penis will instead resemble a small, circular-shaped dot.
Female Kitten Parts
Unlike male kittens, female kittens have little space between the anus and vulva , the urinary orifice. The urinary opening on a female kitten will be shaped like a vertical slit, rather than a circle. Female kittens have nothing resembling a scrotum and will have no testicular bumps beneath the skin under the anus.
The Color Clue
If you're a little squeamish about peeking under your kitten's tail, that cute fuzzy coat can be another clue to kitty's sex. Statistically, tricolor kittens are nearly always female. Ginger-colored kittens can be female but are usually male.