Why is this important?
It is remarkably hard to tell boy and girl kittens apart - at least until they reach puberty (about six months old) at which point it's usually a bit too late...! In this quick guide, we'll look at some of the simple ways you can tell whether it's a boy or a girl, in a species that's rather shy about disclosing the matter. All of the methods below are possible ways to tell a cat's sex; however, some are more useful in kittens than others.
(1) Coat Colour
Although coat colour may be indicative, it isn't usually reliable. Yes, ginger cats are more likely to be toms, but there's no reason you can't get a ginger queen, it's just less common. The only exception is with Tortoiseshell cats, which are almost invariably female (the genes for tortie-ness cannot be found in the male). However, there are a few male torties out there due to genetic or chromosome abnormalities, so even with these, it isn't 100%.
(2) Face shape and build
When adult, tomcats usually have a leaner, more muscular build, and a broader, heavier face and skull. However, these features are driven by the sex hormone testosterone, and don't appear until puberty (in the same way that you wouldn't expect a small boy to have a deep voice and a beard!). In kittens before puberty, there is no significant difference in build or facial shape.
(3) Presence of a penis
This sounds the easiest way - however, tomcats have a retractable penis that points backwards underneath the tail... In exactly the same place as the queen's vulva. In both sexes, it just looks like a small hole underneath their anus.
(4) Presence of testicles
By definition, only the boys have testicles! These are located BELOW the anus but ABOVE the penis (bottom hole), and in most kittens will be about the size of a small pea. You can usually feel them by gently feeling the area with your fingers. However, some kittens are a little shy, and pull their testicles back inside, so while the presence of testicles proves that its a boy, the absence doesn't prove that it's a girl. Of course, the older he is, the more likely it is that they'll be obvious, and by 6 or 7 months, 99% of toms will have fully descended and obvious testicles.
(5) The Ano-Genital Distance
In other words, the distance between the top and the bottom hole. In general, females have a shorter distance than males, but it can be hard to judge unless you've got a couple of kittens to compare!
(6) The Genital Orifice
In the females, this (the bottom hole under the tail) is an elongated slit, so when looking from behind they have a round anus and long vulva, like - an i The toms, meanwhile, have two round holes, like :
(7) Genetic Testing
OK, this is a cheat - but it is an option if all else fails!
No one method is ideal; however, by using a combination of different features, it's almost always possible to sex even very tiny kittens with a fair degree of accuracy. If in doubt, talk to your vets' and a vet or nurse will show you!