When Do Cats Stop Growing?

When you bring home a kitten, know that they won’t stay tiny forever. But when do cats stop growing? 

Understanding when kittens stop growing and reach their final adult size is important for a few reasons. For one, it’s important for timing the switch from kitten food to adult food, because your cat requires a different balance of nutrients when they’re actively growing than when they’re maintaining their adult body condition.

Knowing how big your cat will get will also help you prepare for their needs as a full-grown feline and make sure you have enough space and resources for your kitten when they become an adult. 

When Are Cats Full-Grown?

On average, the typical cat reaches their adult size by 12–18 months of age, but this can vary by both sex and breed. 

Female cats are usually done growing by about 10–12 months of age, while male cats tend to continue to grow until closer to 18 months of age in some cases. 

This is especially true for spayed and neutered cats. Growth is determined by growth plates at a cat’s joints, which cause bones to lengthen. When these plates close, the bones stop growing. The plates’ closing is often delayed in spayed and neutered cats, allowing them to grow for longer.

In larger breeds like the Maine Coon and Norwegian Forest Cat, kittens can continue to grow until they’re 2 years old, or even later in some individuals. Smaller cat breeds like the Singapura may stop growing by 9 months of age or sooner. 

Using these guidelines can help you predict a general time frame around when your kitten will stop growing. However, each cat is an individual and their growth can vary. 

When your kitten is around 12–18 months old (or older, if they are a larger cat breed), their height, nose-to-tail body length, and weight will more or less plateau. You can confirm this by measuring and weighing your kitten on a pet scale every few weeks. 

When your fur baby has maintained the same height, length, and weight on a consistent diet and exercise regimen for several months, you can feel fairly confident that your kitten is done growing. Your veterinarian can also confirm this by inspecting your cat’s joints and even taking X-rays to look at their bone structure.

How Big Will My Cat Get?

If you have more information about your kitten’s parents, the average of the mother’s and father’s adult size and weight can give you some idea of how big your kitten will be when fully grown. 

However, adult body size and weight can also depend on the feeding and care your kitten receives. In addition, if you adopted your kitten from a shelter, you might not have information about your fur baby’s feline parents. Your veterinarian can help you monitor your kitten’s development as they grow to determine when they’ve reached their final adult size. 

Taking X-rays of your kitten’s joints throughout the growth period can be a useful tool for predicting their final body weight and size, as the growth plates at the joints can start to close around 4–5 months of age.

Caring for Kittens vs. Adult Cats

The transition from kittenhood to adulthood is an important time in your cat’s life for many reasons, because caring for kittens is different from caring for adult cats. 

Nutrition

One of the most notable differences in care is the switch from kitten food to adult cat food. 

To support a kitten’s growing body, kitten food often has more calories per cup and more fat and protein than adult cat food. Kitten food also has a different balance of calcium and phosphorus to support bone growth. 

Knowing the right time to switch your kitten to an adult diet ensures your cat receives the right mix of nutrients for their body’s needs while maintaining a healthy weight. Talk to your vet about the right time to transition and which vet-approved adult cat food you should offer.

Vet Care

Veterinary care can also differ between kittens and adult cats. Most kittens, especially early on in life, will need to see their veterinarian every three to four weeks for vaccine boosters until they are about 16–18 weeks old. 

You may choose to continue having your kitten seen at regular intervals during their first year of life to monitor body condition and growth to ensure they’re progressing normally at every stage. By the time your cat is 1 or 2 years old, they should only need to be seen yearly for wellness exams and preventative care.

Dental Care

Closely tied to feeding and veterinary care is dental care for your cat. 

Younger kittens typically have a lower rate of tooth and gum disease than older cats, but this is a great time to get your kitty used to at-home dental care. Make daily tooth-brushing a routine for your cat, as this becomes even more crucial as they become an adult. 

It’s estimated that up to 50–90% of cats older than 4 years of age have some form of tooth or gum disease, and dental issues can start as early as 2 years old in some cats. 

Activity and Supervision

The transition from kittenhood to adulthood can also see changes in overall activity level and the need for supervision. As your kitten settles into adulthood, they may experience a slight decrease in energy level and require slightly less activity during the day to fulfill their needs. 

This is not to say that young adult cats don’t require exercise or mentally stimulating activities—just that they might not run around your home quite as much as they did as growing kittens. 

As cats mature, they might also require less constant supervision as they learn what’s acceptable behavior and lose some of that kitten curiosity that causes them to climb and chew everything they can. 

In general: 

• Kittens younger than 4 months old should not be left alone longer than four hours.

• Kittens 5–6 months old should not be left alone more than five to six hours.

• Kittens older than 6 months should not be left alone more than eight hours at a time.

• Adult cats might be able to be home alone for longer than eight to 12 hours at a time, but they still need company and care to thrive.