What does a boy cat look like, and how do you tell a male cat from a female? It is one of the most common, and surprisingly tricky, questions for new cat and kitten owners, because you cannot reliably tell a cat’s sex from its face or size alone. The answer lies under the tail, in the shape of the genital opening and how far it sits from the anus, plus, in intact males, the tell-tale testicles. This guide explains exactly how to tell a cat’s gender in males, females, and kittens, what the anatomy looks like, the colour clues (like why calicos are almost always female), the general male-versus-female differences, and what to do if you still can’t tell.
Knowing the sex helps with care and neutering. See cat breeds and traits, checking a found cat or kitten, and what caring for a cat involves, and explore more on the Waldev homepage.
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The key: look under the tail
Before the specifics of male and female, the single most important thing to know is where to look, because unlike some animals, you cannot reliably sex a cat from its appearance, size, or face; the answer is under the tail.
The reliable way to determine a cat’s gender is to gently lift the tail and look at the two openings underneath and, crucially, at their shape and the distance between them. When you lift the tail, you will see the anus at the top (just below the base of the tail) and, below it, the genital opening. Two features distinguish the sexes: the shape of the genital opening (round in males, a vertical slit in females) and the distance between the anus and that opening (greater in males, smaller in females). In intact males there is also the scrotum (testicles) sitting in the gap between the two. This shape-and-spacing check is the standard, dependable method used by owners, breeders, shelters, and vets alike, far more reliable than trying to guess from the cat’s overall look, since coat, size, and face are not definitive (though colour gives clues, covered later). To do the check, choose a moment when the cat is calm and cooperative, and gently raise the tail without forcing anything; many cats tolerate a quick look, especially if relaxed. Doing it just after a meal or a nap, when the cat is content, tends to work far better than grabbing a cat that would rather be elsewhere. A memorable shorthand many people use is that a male’s anus-and-round-opening looks like a colon ( : ), while a female’s looks more like an upside-down exclamation mark or a lowercase ‘i’ (the slit sitting close under the anus). With that framework, the sections on males and females below simply fill in the detail. So the essential first step in telling a cat’s gender is to look under the tail at the shape of the genital opening and its distance from the anus, which is what actually reveals the sex. Once you have done it a couple of times, the check becomes quick and second nature, even on a lively cat.
What a boy cat looks like
So, to the headline question directly: when you look under the tail of a male cat, here is exactly what you see, and how it differs from a female.
Under the tail of a boy cat, the genital opening (the penile opening) is round, appearing as a small circle or dot, and it sits noticeably further away from the anus than in a female, so there is a clear gap between the anus and the genital opening. In an intact (un-neutered) male, that gap is occupied by the scrotum, which holds the testicles and appears as a rounded, often furry bulge or a pair of small swellings between the anus and the penile opening, an unmistakable sign of a male cat once you know to look for it. Putting these together, the classic ‘boy cat’ pattern under the tail is: anus at top, then (in an intact male) the scrotal bulge, then the round genital opening set well below, with the whole arrangement spread over a greater distance than in a female. The colon ( : ) analogy captures the two round-ish features (anus and round opening) with space between them. Even in a neutered male, whose testicles have been removed so there is no scrotal bulge, the round shape of the genital opening and the greater distance from the anus usually remain as reliable indicators of a male. So a boy cat, viewed under the tail, is characterised by a round genital opening positioned further from the anus, with a visible scrotum in between if the cat is intact; those features, the round opening, the wider spacing, and (if present) the testicles, are what a male cat ‘looks like’ where it counts. Comparing this with the female pattern next makes the distinction clear.
What a girl cat looks like
To recognise a boy cat, it helps to know what a girl cat looks like by contrast, because the two patterns are quite distinct once you can compare them side by side.
Under the tail of a female cat, the genital opening (the vulva) is a vertical slit rather than a round circle, and it sits close to the anus, with only a small gap between the two. So instead of the male’s round opening set well below the anus, a female shows a narrow, up-and-down slit positioned just beneath the anus with little space in between. There is, of course, no scrotum or testicles in a female. This is the origin of the popular shorthand that a female’s under-tail pattern looks like an upside-down exclamation mark, or a lowercase ‘i’, the anus as the dot and the slit-shaped vulva close below it, or, in the punctuation comparison, more like a semicolon or ‘i’ than the male’s colon. The two most useful distinguishing features, then, are the shape of the opening (round in a male, a slit in a female) and the distance from the anus (greater in a male, smaller in a female), and of these, the distance is often the single most reliable clue, especially in kittens and neutered cats where the other signs are subtler. Seeing a known male and a known female side by side, or comparing with clear photos, makes the difference much easier to recognise. So a girl cat, under the tail, has a slit-shaped genital opening set close to the anus and no testicles, which contrasts clearly with the boy cat’s round opening, wider spacing, and (if intact) scrotum; keeping the two patterns in mind together is the key to confident sexing. Many people find that having seen one clear example of each, the difference is obvious from then on.
Testicles and neutering
Because the presence or absence of testicles is such a clear sex signal, but one that neutering changes, it deserves its own explanation so you do not misread a neutered male as a female.
Intact (un-neutered) male cats have testicles held in a scrotum, which are usually visible under the tail as a rounded, often furry bulge (two small swellings) sitting between the anus and the penile opening, and in an adult tom these are fairly obvious once you know to look. In male kittens the testicles are smaller and less noticeable but typically descend and become apparent as the kitten grows, they are usually descended by around two months of age and grow more prominent over the following months. This is one reason very young male kittens are sometimes mistaken for females before their testicles become obvious. The presence of these testicles is a definitive sign of a male cat. The important caveat is neutering: a neutered (castrated) male has had his testicles surgically removed, so a neutered male will not have a visible scrotal bulge, the area appears flat or empty. This means the absence of testicles does not indicate a female, a very common mistake, since a neutered male also lacks them. This trips up a lot of new owners, who assume a cat with no visible testicles must be a girl. For a neutered male, you fall back on the other clues: the genital opening is still round, and it still sits at the greater, male-typical distance from the anus, both of which distinguish him from a female’s slit-and-close-spacing pattern. So testicles are a clear giveaway of an intact male, but their absence could mean either a female or a neutered male, so you must then use the shape and spacing of the openings to tell which, remembering that a round opening set well below the anus points to a (neutered) male even without visible testicles.
Do cats have a penis?
Among the frank anatomical questions people ask when learning to sex cats is whether male cats have a penis and what it looks like, so it is worth answering plainly for clarity.
Yes, male cats have a penis, but it is generally not very visible externally, which is why sexing a cat relies on the shape of the genital opening rather than on seeing the penis itself. The male cat’s penis points backward and downward and is normally kept sheathed (retracted), so what you actually see under the tail is just the small, round genital (penile) opening, sitting below the scrotum in an intact male, rather than the organ itself. One well-known anatomical fact is that the male cat’s penis is covered in small, backward-pointing barbs or spines; these are entirely normal and serve a reproductive function (they play a role in stimulating ovulation in the female during mating). You would not normally see these in everyday life. Female cats do not have a penis; their external genital opening is the vulva, which appears as the vertical slit described earlier, set close to the anus. In practical terms, when you are sexing a cat you are not usually examining the penis directly at all, but reading the shape of the genital opening, round in males, slit-like in females, together with the spacing from the anus and the presence or absence of testicles. This is why the round-versus-slit shape of that little opening ends up being the detail everyone learns to focus on. So to answer directly: yes, male cats have a penis (normally sheathed, with a round external opening and, as a curiosity, backward-facing barbs), while females have a vulva (a slit), and it is the appearance of these openings, not the penis itself, that you use to determine a cat’s sex.
Telling a kitten’s gender
Sexing kittens follows the same principles as adults but is genuinely harder when they are very young, so it is worth covering how to do it and when it becomes easier.
Kittens are sexed the same way as adult cats, by gently lifting the tail and examining the shape and spacing of the openings underneath, but the differences are subtler and harder to read in very young kittens. In a male kitten, the genital opening is round and set further from the anus (the greater distance being the most useful clue), and the developing testicles may sometimes be felt as tiny bumps in the gap between; the pattern is often likened to a colon ( : ). In a female kitten, the genital opening is a slit set close to the anus, more like a lowercase ‘i’ or upside-down exclamation mark. The single most reliable feature in kittens is the distance between the anus and the genital opening: it is consistently greater in males than in females, so comparing that spacing, ideally between littermates or against a known example, is the best guide. Because these differences can be very hard to judge in newborns and tiny kittens, sexing is easier and more accurate from around six to eight weeks of age, by which point the spacing is clearer and a male’s testicles may be beginning to show. If you are unsure, and many people are with young kittens, a vet or an experienced shelter or rescue worker can confirm a kitten’s sex quickly and reliably. So to sex a kitten, use the same under-tail check with special attention to the spacing (wider gap means male), be aware it is tricky in the very young, and wait until, or check again at, around six to eight weeks when it becomes much easier to tell.
Colour clues (calico, ginger)
While anatomy is the definitive test, a cat’s coat colour can offer a useful hint about its likely sex, thanks to some fascinating genetics, though colour is only a clue, not a certainty.
Certain coat colours and patterns are strongly linked to sex because the genes controlling some colours sit on the X chromosome. The most famous example is that almost all calico cats (tricolour, patched with white, black or brown, and orange or ginger) and tortoiseshell cats (mottled black or brown and orange) are female. The reason is genetic: displaying both black and orange coloration in the coat generally requires two X chromosomes, and since females are XX and males are XY, only females normally have the genetic makeup to show both colours together. Male calicos and tortoiseshells do exist but are very rare, arising from an unusual XXY chromosome arrangement, and they are usually sterile. This rarity is part of why a male calico is considered such an unusual and interesting cat. So if you see a calico or tortoiseshell cat, it is almost certainly female. The flip side involves ginger (orange or red) cats: these are more often male than female, roughly two-thirds to three-quarters of ginger cats are male, again because of how the orange gene works on the X chromosome, though plenty of ginger females do exist, so it is a tendency rather than a rule. Most other colours, black, grey, white, brown, and the various tabby patterns, are not sex-linked and appear about equally in both males and females, giving no clue to sex. So coat colour offers useful odds, a calico or tortie is almost certainly female, and a ginger cat is more likely (but not certainly) male, but because exceptions exist, colour is only a hint, and to be sure of a cat’s sex you still need to check the anatomy under the tail.
Male vs. female differences
Beyond the anatomy used to sex them, people often wonder whether male and female cats differ in size, looks, or behaviour, and there are some general tendencies, though they are influenced heavily by neutering and by individual personality.
There are some broad physical and behavioural differences between male and female cats, with the important caveat that individuals vary and that neutering or spaying reduces many of the sex-linked traits. Physically, male cats tend to be larger and heavier than females of the same breed, and intact (un-neutered) toms in particular often develop a more robust, stocky build, with prominent ‘stud jowls’ (fuller, rounder cheeks) and a thicker neck, alongside the visible testicles; females are usually somewhat smaller and finer-boned. Behaviourally, intact males are more prone to hormone-driven behaviours such as roaming widely, territorial spraying (marking with strong-smelling urine), fighting with other males, and increased vocalising, while intact females go through heat cycles (seasons) periodically, during which they typically become very vocal, restless, and affectionate and may also try to escape to find a mate. Crucially, neutering males and spaying females greatly reduces or eliminates most of these hormone-driven behaviours, spraying, roaming, fighting, and heat cycles, so a neutered or spayed cat of either sex is generally calmer, and the behavioural differences between the sexes become much smaller. On personality and affection, it is worth stressing that the common belief that one sex is more loving or friendly than the other is not reliable; a cat’s individual temperament, early socialisation, and neuter status matter far more than whether it is male or female. So while males tend to be larger and, when intact, more territorial and roaming, and females smaller and subject to heat cycles when unspayed, neutering and spaying narrow these differences considerably, and personality remains highly individual regardless of sex, so choose or judge a cat on the individual, not on assumptions about its gender. Plenty of affectionate lap cats are toms, and plenty of independent, aloof ones are females, which shows how little the stereotype holds up.
If you still can’t tell
Finally, sexing a cat is not always easy even with the right method, so it is reassuring to know what to do if your own check leaves you uncertain.
If, having looked under the tail, you still cannot confidently tell your cat’s sex, you are far from alone, it can genuinely be difficult, especially with young kittens, very fluffy cats (whose fur obscures the area), neutered males (no testicles to give it away), or a wriggly, uncooperative cat that will not stay still. The simple and definitive solution is to have a vet check, as they can determine a cat’s sex quickly and reliably in moments, and getting it right matters, since the cat’s sex is relevant to neutering, health care, and general management. A few tips can improve your own attempt: check when the cat is calm and relaxed rather than struggling; gently lift the tail and look (and, in adults, carefully feel) for the round opening, wider spacing, and any scrotum of a male versus the slit and close spacing of a female; and compare what you see with clear reference photos or, ideally, with a cat of known sex for contrast. Keep the two rules in mind: shape and distance (round opening plus a bigger gap, and any testicles, means male; a slit close to the anus means female), and the colour odds (calico or tortie almost certainly female; ginger more likely male). But if any real doubt remains, do not guess, particularly when it matters, such as before arranging neutering, because getting the sex wrong causes confusion; instead, let a vet or an experienced shelter or rescue worker confirm it, which they can do easily. So when the DIY check leaves you unsure of your cat’s gender, a quick professional check settles it for certain, and that is always the sensible route rather than guessing. There is no shame in asking; even experienced owners sometimes need a second opinion on a tricky kitten.
Frequently asked questions
What does a boy cat look like, and how do I tell a cat’s gender?
The most reliable way to tell a cat’s gender is to look under the tail at the shape and spacing of the openings. Gently lift the tail: you will see the anus at the top and the genital opening below it. In a male (boy) cat, the genital opening is round (like a small circle or ‘o’), and it sits further away from the anus, with a noticeable gap between them, and in an intact (un-neutered) male there is usually a scrotum (containing the testicles) in that gap, appearing as a rounded, sometimes furry bulge. People often describe the male’s anus-and-round-opening pattern as looking like a colon ( : ). In a female (girl) cat, the genital opening is a vertical slit (rather than round), and it sits closer to the anus, with only a small gap, so the pattern looks more like an upside-down exclamation mark or a lowercase ‘i’. So a boy cat, under the tail, has a round genital opening set further from the anus (with a scrotum between if intact), while a girl cat has a slit-like opening close to the anus, and this shape-and-spacing check is the standard way to determine a cat’s sex.
Do male cats have visible testicles (balls)?
Yes, intact (un-neutered) male cats have testicles, held in a scrotum, which are usually visible as a rounded, often furry bulge under the tail, between the anus and the penis opening. In an adult intact tom, the scrotum and testicles are fairly obvious once you know to look, appearing as two small rounded swellings below the anus. In young male kittens the testicles are smaller and less obvious but usually descend and become visible/palpable as the kitten grows (typically the testicles are descended by around 2 months of age, becoming more prominent by a few months old). Neutered (castrated) male cats, however, have had their testicles removed, so a neutered male will not have visible testicles, the scrotum area is flat or empty, though the wider spacing between the anus and the (round) genital opening usually remains as a clue to the cat being male. So intact male cats do have visible testicles (a scrotal bulge below the anus), which is a clear sign of a boy cat, while neutered males lack them, so absence of testicles does not mean a cat is female, you then rely on the shape and spacing of the openings.
Do cats have a penis?
Yes, male cats have a penis, though it is usually not very visible externally because it points backward/downward and is normally sheathed, so what you typically see under the tail is just the small round genital (penile) opening rather than the penis itself. The male cat’s genital opening is round and sits below the scrotum (in an intact male). A notable anatomical fact is that a male cat’s penis is covered in small backward-pointing barbs (spines); these are normal and play a role in reproduction. Female cats, of course, do not have a penis; their genital opening is the vulva, which appears as a vertical slit set close to the anus. In everyday terms, when checking a cat’s sex you are not usually looking at the penis directly but at the shape of the genital opening (round in males, slit-like in females) and the spacing from the anus. So yes, male cats have a penis (with the round opening you see under the tail, and normally-sheathed, barbed anatomy), while females have a vulva (a slit), and it is the shape and position of these openings that lets you tell the sexes apart.
How can I tell a kitten’s gender?
Kittens can be sexed the same way as adults, by the shape and spacing under the tail, but it is trickier in very young kittens and gets easier as they grow. Gently lift the kitten’s tail and look at the two openings: in a male kitten, the genital opening is round and set further from the anus (the greater distance is the key clue, often described as looking like a colon ‘:’ ), with the developing testicles sometimes felt as tiny bumps in between; in a female kitten, the genital opening is a slit set close to the anus (looking more like a lowercase ‘i’ or an upside-down exclamation mark). The distance between the anus and the genital opening is the most reliable feature: it is greater in males than in females. This can be hard to judge in newborns, so sexing is easier and more accurate from around 6 to 8 weeks of age, when the differences are clearer and a male’s testicles may start to become apparent. If you are unsure, a vet can confirm a kitten’s sex. So to sex a kitten, check the shape and, especially, the spacing under the tail (wider gap = male), which becomes easier to read as the kitten reaches a few weeks old.
Do coat colours indicate a cat’s gender?
Certain coat colours and patterns are strongly linked to a cat’s sex, because the genes for some colours are carried on the X chromosome, though colour is only a clue, not a definitive test. The clearest link: almost all calico (tricolour: white, black/brown, and orange/ginger patched) and tortoiseshell (mixed black/brown and orange) cats are female. This is because displaying both black and orange in the coat generally requires two X chromosomes (XX = female); males (XY) usually show only one of those colours. Male calicos and torties do occur but are very rare (and usually sterile), the result of an unusual XXY chromosome arrangement. Conversely, orange/ginger (red) cats are more often male than female, roughly two-thirds to three-quarters of ginger cats are male, because of the way the orange gene works on the X chromosome, though plenty of ginger females exist too. Other colours (black, grey, tabby, white, etc.) are not sex-linked and occur in both sexes about equally. So coat colour gives useful odds, a calico or tortoiseshell is almost certainly female, and a ginger cat is more likely male, but it is not a certainty (rare exceptions exist), so to be sure of a cat’s sex you still check the anatomy under the tail.
Are there other differences between male and female cats (size, behaviour)?
Yes, there are some general tendencies, though individual cats vary and neutering/spaying reduces many sex-linked behaviours. Physically, male cats tend to be larger and heavier than females of the same breed, and intact (un-neutered) toms often develop a stockier build with prominent ‘stud jowls’ (fuller cheeks) and a thicker neck, along with the visible testicles. Females are usually a bit smaller and finer. Behaviourally, intact males are more prone to roaming, territorial spraying (marking with strong-smelling urine), fighting with other males, and vocalising, driven by hormones, while intact females come into heat (season) periodically, becoming very vocal, affectionate, and restless. Crucially, neutering males and spaying females greatly reduces or eliminates these hormone-driven behaviours (spraying, roaming, fighting, heat cycles), so a neutered/spayed cat of either sex tends to be calmer and the behavioural differences between the sexes become much smaller. As for affection and personality, the stereotype that one sex is more affectionate is not reliable, individual personality, upbringing, and whether the cat is neutered matter far more than sex. So males tend to be larger and, if intact, more territorial and roaming, females smaller and subject to heat cycles if unspayed, but neutering/spaying narrows these differences, and personality is highly individual regardless of sex.
What if I still can’t tell my cat’s gender?
If you cannot confidently determine your cat’s sex from looking, which can genuinely be tricky, especially with young kittens, fluffy cats, neutered males (no testicles), or a wriggly, uncooperative cat, the simple solution is to have a vet check, as they can quickly and definitively confirm the sex. It is worth getting it right, as knowing the sex matters for neutering, health, and care. A few tips can help your own check: do it when the cat is calm and relaxed (not struggling), gently lift the tail and look (and, in adults, gently feel) for the round opening and wider spacing plus scrotum of a male versus the slit and close spacing of a female, and compare with pictures or, ideally, with a cat of known sex. Remember the shape-and-distance rule (round opening and bigger gap = male; slit and small gap = female) and the colour clues (calico/tortie almost always female; ginger more often male). But if any doubt remains, do not guess, especially for anything important like arranging neutering; a vet or an experienced shelter/rescue worker can tell you for certain in moments. So if you are unsure of your cat’s gender, a quick vet visit (or check by an experienced person) settles it reliably, which is the sensible route whenever the DIY check leaves you uncertain.
The quick version
What does a boy cat look like? You tell a cat’s sex by looking under the tail at the shape and spacing of the two openings. A male (boy) cat has a round genital opening set further from the anus, with a scrotum (visible testicles) in the gap if he’s intact, the pattern is often likened to a colon ( : ). A female (girl) cat has a slit-shaped genital opening set close to the anus and no testicles, likened to an upside-down exclamation mark or ‘i’. The distance between the anus and opening is the most reliable clue (wider = male). Male cats do have a penis (normally sheathed, with the round opening you see, and naturally barbed). Neutered males have no testicles, so absence of testicles doesn’t mean female, use the round shape and wider spacing. Kittens are sexed the same way but it’s easier from ~6-8 weeks. Colour hints: calico and tortoiseshell cats are almost always female; ginger cats are more often male, but colour is only a clue. Males tend to be bigger (intact toms have jowls, spray, and roam); neutering/spaying narrows sex differences, and personality is individual. If unsure, ask a vet, they’ll confirm it in moments.
For more, see cat breeds and traits, checking a found cat or kitten, and what caring for a cat involves. Browse the full cat blog, the pet calculators, and more free tools on the Waldev homepage.
Note: This guide is for general education. Sexing cats, especially young kittens, fluffy cats, and neutered males, can be genuinely difficult; if you are unsure, have a vet or experienced shelter/rescue worker confirm the sex, particularly before arranging neutering. Handle cats gently when checking and do not force a struggling cat. Neutering and spaying are recommended for health and behaviour; consult your veterinarian about your cat’s sex, neutering, and care.
A cat’s sex is read under the tail from the shape (round vs slit) and spacing of the openings, plus testicles in intact males. Pet owner resources →
If you cannot tell a cat’s or kitten’s sex, a vet can confirm it quickly, useful before arranging neutering. Locate a hospital →