At four weeks old, kittens are developed enough that you can reliably identify their sex by examining two features: the shape of the genital opening and the distance between it and the anus. This is easier than it sounds, especially if you have a litter to compare side by side. Here’s exactly what to look for.
What You’ll See Under the Tail
Gently lift the kitten’s tail and look at the two openings underneath. The first one, right below the base of the tail, is the anus. Directly below that is the genital opening. These two openings are what you’ll use to determine sex, and the differences come down to spacing and shape.
In a female kitten, the genital opening (the vulva) sits very close to the anus. The two openings look like a lowercase “i” or an upside-down exclamation point. The vulva itself appears as a small vertical slit.
In a male kitten, there’s noticeably more space between the anus and the genital opening. That extra distance is where the testicles will eventually develop. The genital opening is also rounder, more like a small dot than a slit. The overall appearance resembles a colon (:) with two round openings spaced apart.
If you’re only examining one kitten, these differences can be subtle. Having littermates to compare makes it dramatically easier because the contrast between males and females becomes obvious when you look at them back to back.
Checking for Testicles at This Age
Don’t expect to see visible testicles at four weeks. They typically aren’t plainly visible until six to ten weeks of age and may not be fully palpable in the scrotum until eight to sixteen weeks. At four weeks, though, you can look for a small raised area or extra tissue between the anus and the genital opening on a suspected male. If you’re unsure, gently press the area between the two openings with your thumb and forefinger. If you feel two tiny, oval-shaped objects beneath the skin, that’s a male. If the area feels flat with no lumps, it’s likely female, though some males simply haven’t descended yet at this age.
What Coat Color Can Tell You
Certain coat patterns are strongly linked to sex because the gene controlling orange versus black pigment sits on the X chromosome. Since females carry two X chromosomes and males carry only one, this creates predictable patterns.
Calico and tortoiseshell kittens (those with patches of both orange and black or brown) are female 99.9% of the time. The rare male calico exists only because of a genetic anomaly where the cat carries an extra X chromosome (XXY). If you have a tortie or calico in the litter, you can be nearly certain she’s female.
Orange tabby kittens skew male, though not as dramatically. A solid orange cat has roughly a 1 in 2 chance of being male, while for females the odds are closer to 1 in 3. So about two-thirds of orange tabbies are male. This isn’t reliable enough to replace a physical check, but it’s a useful clue that can confirm what you’re seeing under the tail.
How to Handle a 4-Week-Old Kitten Safely
Four-week-old kittens are small and still developing their temperature regulation, so keep the exam brief. Talk softly, move slowly, and handle gently. Place the kitten belly-down on a warm, soft surface like a towel, then lift the tail. Some people find it easier to hold the kitten upright under the armpits with one hand and use the other to lift the tail, but only do this for a few seconds at a time.
If the kitten squirms or cries, put it back with its mother and try again later. You don’t need to rush. If fur is obscuring the area (common in longer-haired breeds), you can use a dry, soft tissue to gently part the fur around the genitals for a clearer view. Avoid using water or anything wet, which can chill the kitten.
When You’re Still Not Sure
Even experienced breeders occasionally misidentify kittens at this age. If you’re not confident after checking, wait a week or two and look again. The differences become more obvious every week as the kitten grows. By six to eight weeks, the spacing difference between males and females is pronounced, and in males you’ll start to see the scrotal area filling out. A veterinarian can confirm sex quickly at a routine first visit, which typically happens around the same time frame.