When Are Cats Fully Grown?

When Are Cats Fully Grown?

Kittens are fluffy, playful creatures that every cat lover adores. But these little creatures grow up to become adult cats who can be loving companions and lifelong friends to their humans. With how playful and mischievous they are, it can be difficult to wait for them to grow up.

Cats are considered fully grown at twelve months but will reach their adult size anywhere from eight to twelve months. A female kitten that has reached at least six months will begin going into heat, signaling male cats that she is ready to mate and procreate.

If kittens are given the right environment to grow up healthy, they will be healthy for life. Let’s keep going to find out how to care for your growing kitten.

Cats Reach Full Size at 12 Months

Kittens grow exponentially for the first six months of their lives, which is the equivalent of an adolescent human being. At this age, the kitten becomes sexually mature and ready to start procreation. But they don’t reach full maturity until they are a year old, or the equivalency to a 21-year old human.When Are Cats Fully Grown?

According to the experts, cats generally stop growing at this age, but some cats continue to grow well past two years of age. The Main Coon breed stops growing at two years old, as well as other larger breeds of domesticated cats.

When cats spend most of their time indoors and do not get a lot of exercise and fresh air, they tend to put on more weight, just as with humans.

The Life Stages of a Cat

Until six months old, Kittens have a lot of growing to do, and they meet a lot of milestones relatively quickly. At this time, you need to socialize your kitten with humans and other cats, should you want a multiple-cat household.

By the time they are about three or four months old, their baby teeth start falling out and are replaced with adult teeth. A similar process happens in humans by the time a child is six years old.

Between six and nine months, a kitten becomes sexually mature, and by one year, they are fully grown. But they still act like kittens in many ways and get into a lot of mischief and trouble. Though they are considered adults at this age, they still need to mature mentally. You might notice this when your cat still behaves like a kitten and gets into several things you’d rather not have them get into.

When a cat reaches two years, they are behaviorally and psychologically mature. After three years until six years, a cat is at their healthy prime and settles into their personality and routine at this time.

Cats that have reached seven years until around ten years old, they start slowing down and rest more often than they used to. This stage matches humans when they are in middle age. Later, when a cat starts getting into their double-digit years, their health starts deteriorating and become susceptible to disease and tooth decay.

An indoor cat can live upwards to 20 years, while an outdoor cat lives between two and 11 years, due to how many more dangers live outside of the house. If an indoor cat is mentally and physically active, they can live to the upper end of that limit. But if the cat is mainly sedentary, they might have a shorter life.

What Are the Nutritional Requirements at Each Stage?

As with human babies and children, kittens and cats have specific nutritional needs to grow healthy, strong, and active.

Kittens are weaned off their mother’s milk around six weeks to two months, which at that time, they have enough teeth to eat kitten food. You can either choose to give them dry food or wet food from cans specially formulated for kittens’ growing needs. They also need to eat quite a bit more calories than older cats because of how much they are growing and how active they are.

You can start feeding your kitten adult cat food around ten months old, which again, can be either dry food or canned wet food. However, cats that grow bigger like the Maine Coon or the Bengal should stay on kitten food until two years of age because they are still growing during this time.

If you have an indoor cat, you might look at getting food made for indoor cats. But this is only an option, as most cat food meets all healthy adult cats’ nutritional requirements.

When your cat is around 10-11 years old, their nutritional needs change as their health starts going down, and they need fewer calories than younger cats need. At this point in their lives, you may need to feed them specialized cat food if they have kidney disease or other illnesses that require certain nutrition. Ask your vet about this if you have concerns about your senior cat’s nutritional needs.

How Big Will Cats Get as Adults?

Generally, most cats will grow to between 8 and 15 pounds when they reach adulthood. Some cats will be smaller or larger, depending on their breed, how much they eat as a kitten, and any illnesses they may have during these formative years.

Indoor cats, without a lot of activity, tend to be heavier than outdoor cats. But if you give your cat several places to jump, run, and pounce, they have a way to stay in shape. If there are children in the house, they will naturally get your cat to play, which keeps both of them active, even indoors.

Larger breeds, like the Bengal cat, grow to the upper adult cat limit at 15 pounds or more, and they are 13-16 inches long or more. They are very muscular and can jump further than other cats’ breeds and have a clear spotted coat. Savannahs are also very large and take up to two years to grow to their full size.

How to Keep an Indoor Cat Healthy

Indoor cats tend to be more sedentary because they aren’t running from outdoor predators or chasing prey. But that doesn’t mean they have to stay sedentary, even in a small house. You can use a laser pointer for them to chase but never catch. Other tips to keep your cat healthy are:

  • Using a string, hold it over them on a wall and encourage them to jump and catch it.
  • Throw a cat toy to the other side of the room or house and have them bring it back to you, much like a game of fetch. (Some cats will play fetch, by the way.)
  • Use restraint when feeding them and follow feeding guidelines according to their age and breed.
  • Provide toys that encourage play and their hunting instincts so they don’t get bored or anxious.

Indoor cats can be just as healthy as outdoor cats when given the right elements.


Kittens are usually in high demand because of their sweet natures, but eventually, they grow up and become elegant cats, and very quickly for that matter. When their needs are provided for and have multiple chances for proper socialization, they will grow up to be loving companions who will give you lots of snuggles and love.

Shelter cats, however, tend to be on the small end of the size scale because they are not fed as much as they need for proper growth. However, when a cat is rehomed, they can make up that size and become a healthy full-grown cat.