When Are Cats Considered Adult?

When Are Cats Considered Adult?

Cats may not have nine lives, but they do have very long ones. The average lifespan of an indoor cat is 17 years old! But when are they considered adults, and when do they stop growing?

Cats are considered adults at 12 months of age. However, they will continue growing until they reach full size; this can be between 18 months to four years old. They reach peak mental and physical maturity around four years old.

Read on to learn all about how your cat ages, what happens during cat adulthood, and why it’s important to know about your cat’s life span.

Why Is It Important To Know When Your Cat Is an Adult?

It is important to know when your cat is an adult, so you know if they are maturing properly. Using the standard aging of a cat will help create timelines and milestones for your training. For instance, kittens learn how to use the litter box at a very young age, and by the time they are an adult, they should know their name–even if they don’t respond to it.

How Do Cats Age Compared to Humans?

People often say that one human year is equal to seven dog years, but how does this apply to cats? One human year is closer to four cat years, but only after the first two years of the cat’s life. That sounds tricky, but it’s because cats develop so quickly during their first year of life. Let’s break this down a little more.

Year One

The first year in a cat’s life is equivalent to the first sixteen years in a human’s life. The rapid development and rate at which kittens reach sexual maturity are like an expedited childhood and adolescence for humans. Whereas a human takes years to go through puberty, a kitten does this in a matter of months. A one-year-old cat is equal to a sixteen-year-old human.

Year Two

The second year in a cat’s life is similar to the next five years in a human’s life, after 16. Cats fly through their second year of life, experiencing their first taste of adulthood. They benefit from higher levels of confidence and physical ability and enjoy freedom as a young adult. A two-year-old cat is equivalent to a 21-year-old human.

Every Year After That

The first two years of the cat’s life see rapid changes and growth, which slow down after that. Each year after the first two years of a cat’s life is equivalent to four human years. Look at the chart below to see how a cat compares to a human throughout its life.

Cat Age (Year/s)Approximate Human Equivalent (Year/s)

From Kitten to Cat

The development from a kitten into a cat is synonymous with the cat becoming an adult. At the age of one year, cats are considered an adult. At this time, you should reassess your pet’s needs for food, exercise, and mental stimulation, as your cat’s activity levels will naturally slow.

While kittens need a rich diet high in calories to assist in their important growth stages, cats don’t have such a high demand for calories, and you’ll need to start tapering their food back. If you don’t properly limit your cat’s food intake, they will slowly start to gain weight as their exercise levels drop.

However, you need to continue with positive reinforcement for your cat as his personality is still developing. If you want a friendly cat, encourage him to meet new people and be held by guests in your home. If you want an adventurous cat, praise him when he goes outside, and if you want a cat that will hunt the little critters on your property, praise him greatly whenever he brings you a “present.”

When Cats Stop Maturing

Kittens reach sexual maturity in their first year of life if they aren’t spayed or neutered very young. They become adults at one year old but continue to grow physically and mature mentally, for long after that.When Are Cats Considered Adult?

Some cats may reach their growth peak at 18 months, while others continue growing for four years. Mental maturity isn’t fully reached until around three or four, when their brains are fully developed, as well as their personalities. It’s important to keep steady training and positive reinforcement until this age, as the cats are still developing.

What Is an Adult Cat?

An adult can is any cat over one year of age. Since indoor cats can live up to 20 years, adulthood is a huge majority of their life, unlike humans who spend ten years in childhood, ten in adolescence, and then enter adulthood. Within a cat’s adult life, there are three main stages.

Prime Adult Life

From ages 1-6 years old, your cat is in the prime of his adult life. He will be at his most spry, brave, and adventurous during these years. If your cat is an outdoor cat, he will roam the farthest during this time and likely bring home a few dead mice or birds. Your cat will still need a healthy diet during this time but lower in fat than when he was a kitten.

Mature Adult Life

From 7-10 years old, your cat is in his “mature adult” phase. His activity levels will steadily drop, and he will spend less time hunting mice and more time lazing about in the sun. You will need to cut his food portions back at this time to prevent him from gaining weight that would be dangerous to his joints and spine.

Senior Adult Life

From 10 years old and onwards, your cat is in his twilight years and is considered a senior. These years can indeed last for an entire decade–especially if he is an indoor-only cat, but his activity levels will drop greatly. Your cat will spend most of his time in warm areas of the house: in piles of fresh laundry, stretched out in sunspots, or curled up in your lap.

When Are Cats Considered Elderly?

Your senior cat will eventually become elderly. It’s important to note that this is more a statement of your cat’s health and is not a completely separate life phase. An elderly cat is still considered to be in its senior adult life.

As your cat becomes elderly, you will see their appetite, activity levels, and sometimes their patience drop. Outdoor cats are generally considered elderly from 13 years onward, while indoor cats are elderly at 15 years, but this varies depending on your cat’s fitness and wellbeing.

At this senior stage of adulthood is when most of your cat’s health issues will arise. Many cats encounter hyperthyroidism, arthritis, and dental disease during this time. Kidney and bladder issues are also common in elderly cats. Elderly cats will also commonly endure hair loss, brittle nails, and dry or patchy skin.


Cats are considered adults quite quickly compared to humans–at just one-year-old. However, they spend a very long time in adulthood, and it is broken up into three stages: prime adult, mature adult, and senior adult.

Even though your cat is considered an adult at one year old, he will not stop developing at this time. This age is equivalent to a 16-year-old human that continues to grow and mature into their 20s. Your cat will reach his peak physical and mental condition between two to three years old.