Adult Cat – At What Age Are Cats Fully Grown?

How do you know if your cat is an adult cat? What is their kitten phase? And if they have reached maturity, what should change and stay the same? 

The bottom line is cats reach adulthood at different stages, depending on their breed and gender. But there are some key growth indicators that you should be aware of to tell whether your cat is an adult. We cover these key milestones and more in this article.

Table of Contents

When Is a Cat an Adult? Key Milestones

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Rapid Growth: 2 to 6 Months

Cats grow rapidly in the first few months of their life until they reach about one-fourth of their adult weight. 

As the kitten grows rapidly, it needs a lot of nutrients to support its growth. On a per-pound basis, kittens require twice as much energy as adults.

Adolescence: 6 to 12 Months

Baby kitten playing

Baby kitten playing

At about six months, kittens start to go through a growth spurt. They need more food and water and usually gain weight during this time. They also develop adult teeth and may begin to sprout fur on their faces and paws. During this phase, kitten food is still the best option for cats as they require quality nutrients. 

Young Adult: 6 Months to 2 Years

It is a time of transition for your cat as they move from being a kitten to an adult.

When your kitten reaches this stage, it may begin exhibiting signs of independence and self-sufficiency, such as wandering around the home.

Prime Adult: 3 Years to 6 Years

Thai cat

Thai cat

In prime adulthood, cats reach their full growth potential and become sexually mature (able to breed). Other signs of maturity include developing territorial instincts, which may lead your cat into aggressive behavior.

Mature Adult: 7 Years to 10 Years

A cat reaches maturity at about seven years of age. They tend to become less active, and some health issues may arise.

Adult cats generally weigh between 6 and 12 pounds, but this can vary depending on breed and sex. Be aware that some breeds are tiny (for example, the Singapura) or very large (such as Maine coon cats).

Older Age: 11 Years to 14 Years

Big old orange cat

Big old orange cat

Cats who have reached the age of 11 or 12 years old may start sleeping more and not be interested in playing as much as they used to. 

They may also begin gaining weight and have increased visits to the litter box. It is normal behavior for older cats, but they must receive regular veterinary examinations, especially if they start showing signs of illness or discomfort.

Essential Factors To Consider in Cat Adulthood

The Cat Breed

Your cat’s breed will affect its growth rate and development. Some breeds of cats can take less time than others to reach adulthood. For example, a Maine Coon or Ragdoll can reach adulthood by eight months, while a Siamese or Russian Blue may not do so until 12 months.


The first year of a kitten’s life is a time when they grow the most. By the time your cat reaches adulthood, it will have doubled its size and tripled its weight. Because they are growing so rapidly, adult cats need high-quality food that contains all the nutrients they need to maintain good health.

The ideal diet for a cat should contain a good amount of protein and essential fatty acids from fish oils. It should also contain carbohydrates and fiber to ensure proper digestion and weight control.


Exercise helps your cat lose weight and maintain a healthy weight as well. Regular playtime with toys can help keep your cat fit and trim while reducing stress levels, which improves overall health.

Been Spayed or Neutered Before Your Cat Reached Adulthood

Cats spayed or neutered early in life tend to grow larger than cats who are not spayed or neutered until they are adults. The ability of neutered cats to burn calories is modified, and they can gain weight rapidly after neutering.


Watching your kitten’s behavior and physical changes, you’ll know when his kitten has reached adulthood. 

Some cats become more confident and outgoing during this stage; others become more reserved. And depending on your cat’s personality traits, you may see an increase in playfulness or aggression.