When Are British Shorthair Cats Full Grown?

The British Shorthair is one of the world’s most popular cat breeds; in their country of origin, British Shorthairs are especially well-loved and perhaps more widely preferred by cat fanciers than any other. It’s not hard to see why: besides being healthy, long-lived and easy to care for, these cats have a charmingly loving nature and very appealing “teddy-bear” looks. A larger breed with a cobby (chunky) configuration, British Shorthair cats continue growing for a number of years and tend to get quite large; they are sturdy, muscular felines with solid characters to match their solid builds.

When are British Shorthair cats full grown? By three years old, most British Shorthair cats have reached their full adult size. Some continue growing for as much as five years. They may gain weight after this age but they won’t grow any larger.

When Are British Shorthair Cats Full Grown?

Perhaps you’re a prospective cat owner who wants to know how large this breed can grow before you buy a kitten. Maybe you already own a British Shorthair cat and want to know how big your cat will get. Maybe you have a new British Shorthair kitten and you want to check that she’s growing properly, or maybe you have a young British Shorthair adult and want to make sure your cat isn’t getting too big. Whatever questions you have about your British Shorthair, we’ve got the answers. Keep reading to find out more about your cat’s weight, growth and health.

Growth in British Shorthairs

When are British Shorthair cats full grown? British Shorthairs grow a lot in their first year of life. Cats of this breed reach most of their adult growth by 12 months of age. They continue growing after this, typically for at least three years and possibly up to five. This breed is categorised as medium-large; they’re not small and dainty creatures.

Female British Shorthairs are very much smaller than male British Shorthair cats — there’s an unusual degree of dimorphism in this breed, much greater than would normally be expected in domestic cats. Note that female British Shorthairs aren’t quite hefty themselves — they’re just a little shorter and lighter than their brothers, although with the chunky, cobby configuration that marks a true British Shorthair.

British Shorthairs: One Or Two?

British Shorthair kittens start out at much the same size; boys and girls have a similar weight at birth and are hard to tell apart. They grow at slightly different rates, however, and by the time you receive your kitten (at 12 weeks or a little older,) there may be a noticeable difference and size between brothers and sisters. British Shorthair kittens will then continue to grow at the rate of — very roughly — 450 kg per month, with boys tending to grow rather faster. While their growth isn’t usually too erratic, British Shorthair cats can experience growth spurts (especially in the first year of life).

Male kittens, in particular, can have a rather interesting pattern of growth, going through several growth spurts before settling down to a slower and steadier growth rate. Male British Shorthairs may also go through a feline version of that lanky phase that adolescent human boys endure, as their bones lengthen rapidly and their muscles struggle to keep up.

british shorthair liliac

By the time British Shorthair cats have reached twelve months of age, they will have reached a large percentage of their adult size. Growth doesn’t stop here, however; it simply slows down and becomes more gradual. Your cat is apt to continue growing for the next two to three years, getting a little longer and taller and packing on more muscle. Between the ages of three and five, British Shorthairs are fully grown and all their charmingly chunky features are properly developed.

How big should my kitten be?

You probably won’t be dealing with a very tiny kitten, as breeders don’t like to part with kittens until they’ve had plenty of time to get used to humans and moved on to solid food. By the time your kitten is 12 weeks old, she should be well-socialised and have developed enough to leave her mother. At this age, your kitten should weigh from a little over 1.4 kg to just over 1.8 kg.

As we’ve previously discussed, British Shorthair kittens put on roughly 450 kg per month. The exact growth rate will vary, with kittens tending to slow down during some weeks and then catch up in others. Some kittens will gain more per month, some a little less.

british shorthair cat

Between six and 12 months, British Shorthairs — especially males — go through the aforementioned “awkward age” where they tend to be rather gangly and clumsy. Think of this as being like your kitten’s teenaged years. Later in this article, we’ll look at this growth stage in more detail. By the end of the first five months, your British Shorthair kitten should be at least 2.3 kg in weight.

I want to buy equipment for my British Shorthair kitten but I think she might outgrow everything. What should I do?

Everything for a full-grown British Shorthair needs to be scaled up for this large breed’s needs.

A scratching post needs to be half again as tall as the length of the cat, tail excluded. I have now 3 British Shorthairs (2 kittens and 1 3 years old male) and must say that a large cat tree like this one (from Armarkat) serves us well. There’s nothing wrong with buying inexpensive kitten-sized equipment for your cat and then replacing some items as she outgrows them. But with something like a scratching post, you may as well go ahead and buy one size for a full-grown cat.

scratching post

Litter-boxes need to be as wide as the cat is long and half again as long as the cat. In the case of a full-grown British Shorthair tom, “half again as long as the cat” could be a clear 75 cm or 30 inches. In my opinion, a large, covered litter box with the front flat works the best for such large cats. Get Catit Hooded Pan and it will serve you for years. Litter-boxes need to be big enough for your cat to use comfortably, but low enough for a kitten to climb in and out of.

What Size Of Litter Box For British Shorthair?

Because she’ll be eating smaller meals, it’s fine to serve her wet food on a small ceramic dish with a larger ceramic bowl for clean drinking water. When your cat is a bit bigger, at six months or so, I would advise swapping out her water dish for a kitty drinking fountain (I have this one: Drinkwell 360 Stainless Steel Pet Fountain) Like most cats, British Shorthairs don’t always drink enough water to be healthy. Drinking fountains encourage cats to drink more water but are sometimes a bit too large for kittens to use easily.

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I think my kitten is too small. Why isn’t she growing?

In general, your kitten should be round but not fat. If she’s a few grams on either side of the healthy weight range for her weight, it’s probably not a problem. If her weight isn’t increasing as expected, she could be dealing with a health issue. A drop in your kitten’s weight is a bad sign and you should seek medical advice. A lack of weight gain can happen if the kitten develops an infection; it can also be a symptom of something more serious, such as anaemia or even a heart problem. Sometimes, though, it’s simply down to a lack of sufficient calories.

Older British Shorthairs sometimes need to have their food intake monitored as they can become prone to obesity, a fact which sometimes leads people to restrict their British Shorthair kittens’ food. This is dangerously misguided, however. It’s important to provide plenty of good-quality food when your kitten is small. She’s growing fast and needs plenty of nourishment. (I’ve never seen an overweight kitten. They run around too much.)

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Personally, I prefer not to supply dry food, especially for kittens — it can promote problems with your pet’s kidneys or urinary tract, especially in small kittens who don’t always drink enough water to make up for the dry food. Wet food, however, should be supplied in small portions: your kitten probably can’t eat much at once and wet food left out can go rancid quickly (Royal Canin Urinary wet food will be ideal.) This means feeding your kitten several times a day; some hungry little babies need five small meals.

I’ve been feeding my kitten frequently but she’s still growing very slowly. What should I do?

Failure to grow and thrive can be down to any number of medical issues; hopefully, if you’ve purchased your kitten from a properly registered breeder and have been taking her to her scheduled vet checkups, any serious problems should have been caught. That said, health isn’t guaranteed in any cat and even the best-cared-for kitten can develop problems that may affect growth.

The first question we need to answer is whether she’s suffering from an underlying condition that needs to be addressed. Take your kitten to the vet and have her checked out. Explain that you’re concerned because she doesn’t seem to be growing properly. If your vet can’t find anything wrong, then I’d turn my attention back to her food. Choose a premium food with a high percentage of protein. Personally, I’m not a fan of special kitten formulas — regular cat food, perhaps mashed a little to make it easier to eat, should be fine after 12 weeks.

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Avoid foods with vegetable filler and look for a brand that’s transparent about its ingredients. Meat used in the food should be named specifically in the ingredients list — “duck flavour” or “rabbit flavour” can be misleading. Cats and kittens have specific nutritional needs: as well as protein they need various vitamins, minerals and amino acids — in particular, taurine. Again, my favourite choice would be Royal Canin urinary.

Avoid giving your kitten milk — after weaning, British Shorthairs become lactose intolerant and milk could upset her stomach. Your kitten should start growing rapidly when given the right food.

Does the Lifespan of British Shorthairs Depend on When They Are Fully Grown?

The british shorthair lifespan is not affected by when they are fully grown. It primarily depends on their genetics, overall health, and the care they receive throughout their lives. With proper nutrition, regular veterinary check-ups, and a safe environment, British Shorthairs can live an average of 12 to 17 years.

My British Shorthair kitten is within the normal weight range but doesn’t have the cobby physique I was hoping for.

We’ve mentioned the feline adolescent period before but let’s take a deeper dive. British Shorthair cats of this age tend to be a bit more rumbustious than a mature British Shorthair, as they act out, test boundaries and get used to their changing physiques. While female kittens seem to mature fairly gracefully in comparison to their brothers, they may still go through a few months where they appear rangy and ungainly. Cats tend to be clumsier during this period — the rapid growth makes it hard to adjust.

What’s happening is that your cat’s bones are lengthening rapidly and the rest of their body is struggling to keep up. Those weaker kittenish muscles and lower fat levels certainly look odd when laid over a more adult skeleton; keep in mind, though, that this is only temporary. Your cat’s musculature will catch up and she’ll develop the familiar round, chunky look of the classic British Shorthair.


You simply need to be patient and ensure that your cat receives good nutrition to support her ongoing development. Don’t be tempted to feed higher-calorie foods to “fatten up” your cat — this can actually be counterproductive, as the empty calories do nothing to support healthy growth and development. If your British Shorthair is within the healthy weight range, there’s really nothing to worry about. This gangly period will generally have passed before your cat reaches her first birthday.

How do I know if my British Shorthair has stopped growing?

Growth slows significantly after the first 12 months but does continue for another two to four years after this period. You probably won’t see any dramatic physical changes after your cat is two years old, although her features will continue to develop. These handsomely stocky cats really grow into their looks between three and five years, as their bodies pack on more muscle and acquire the coveted round and blocky look of a real British shorthair. They will get a little taller and somewhat heavier over the second and third years, with slower growth a couple of years after that.

british shorthair cat

By the age of five, a British Shorthair will have completely finished growing. That doesn’t mean they won’t get any heavier, however. British Shorthairs are somewhat notorious for becoming rather lazy and tending to put on weight if their food isn’t monitored. While younger cats don’t really struggle with their weight, cats over the age of five can really pile on the pounds if you don’t encourage plenty of activity and keep an eye on their diet. In the next section, we’ll discuss healthy weight ranges for male and female shorthairs, as well as ways to prevent obesity in British Shorthairs.

My British Shorthair is over five but still getting bigger. Is she growing?

Not really. British Shorthairs are a notoriously low-energy breed, especially once they outgrow kittenhood and its abundant energy. That’s great in some ways. British Shorthairs are not at all destructive and unlikely to vent their nervous energy by destroying your curtains or furnishings if you don’t keep them entertained. Their more laid-back nature makes cats of this breed calmer, more patient and more gentle than some other breeds. On the downside, it can also lead to ongoing weight gain.

Remember, though, that this breed is not a slender or delicate one — they’re supposed to be solid — and don’t get too hung up on their size. As long as your British Shorthairs are within the healthy weight range for their gender, you don’t need to worry too much; this breed just tends to middle-age spread. One way to tell whether your British Shorthair is getting too heavy is to feel her flanks. Her ribs should be palpable but not too exposed — you should just be able to feel them through her fur. If you have a queen cat, she should probably not get heavier than 5.4 kg. Males should not go much over 7.7 kg.

british shorthair cat

While a true British Shorthair is supposed to be solid, and while chubby cats can be cute, significant weight gain can cause health problems and affect your pet’s well-being. Obesity in cats can cause problems with their joints, heart conditions, high blood pressure and other issues that make life less enjoyable for them. British Shorthairs seem especially prone to this sort of issue; they become sedentary in later life and generally have big appetites. To get around this, you can encourage your British Shorthair to be more active with toys and games while ensuring that they don’t overdo it at mealtimes. Once your cat reaches 12 months old, you can reduce the number of meals to two portions of quality food a day.

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