Cat Tips

When Do Kittens Become Cats? 

Kittens grow up much faster than human babies do, but have you ever wondered when your kitten is officially considered an adult cat? Kittens have different needs than adult cats do. It’s important to be able to know when they make the change from kittenhood to adulthood.  

Which Age is Considered Fully Grown? 

The age at which your kitten can be considered a full-grown adult cat isn’t as black and white as you may expect. However, most experts agree that the majority of kittens can be considered adult cats at 12 months of age or at their first birthday. However, this doesn’t mean your cat is fully grown yet. In fact, your cat will continue growing muscle and filling out their adult frame until they are around 18 months old.  

 If you have a larger breed cat, such as the Maine Coon, they may not be fully grown until they are around two years old. Basically, there isn’t a specific age at which cats are done growing universally. However, most people consider a one-year-old kitten an adult cat.  

Kitten Growth Stages 

The first six months of your kitten’s life involve a lot of growing and changing. If you have a cat from birth, these are all of the major milestones you can expect them to reach during the first half-year of their life.  

  • Week Two: Most kittens will open their eyes 

  • Week Three: Ear canals are fully open 

  • Week Four: Baby teeth begin coming in, and kittens are able to begin exploring their surroundings 

  • 8 to 12 Weeks: Kittens can get their first vaccinations and are old enough to be separated from their mothers if you desire.  

  • Month Four: Baby teeth begin falling out and getting replaced by adult teeth; this process is done by around seven months old.  

  • 5 to 6 Months: Most kittens are now big enough to be safely spayed or neutered 

After month six, your kitten will be close to their full adult size but not quite there yet. The growth rate for kittens between six and 12 months of age is slower than that of the first six months, but they still aren’t considered adult cats until they hit the one-year mark.  

 Adult Cat Stages 

As your kitten matures into an adult, their growth and change rate will slow down. However, your cat will continue to experience different stages of their life throughout adulthood. Here’s a look at the normal life stages of your housecat.  

  • Junior (eight months to two years): Cats are finishing up their growth into adulthood during this stage and tend to be just as playful as they were as younger kittens. It’s important to make time to play with your cat regularly during this stage.  

  • Prime Adult (two to six years): Your cat is fully grown and is in what is considered the “prime” of their life, with plenty of energy and health.  

  • Mature Adult (six to ten years): During these years, your cat will start to be less active. It’s important to keep an eye on their diet and exercise because it becomes easier for them to gain too much weight, leading to health issues.  

  • Senior (10 to 14 years): At this point, it’s important to take your cat to the vet regularly, as health issues tend to be more common during the later years of your cat’s life. Doing all you can to keep them happy and healthy will let them enjoy their senior years. 

 Although your cat isn’t growing after about a year and a half, there are still many changes to experience with them throughout their life. Knowing what each stage holds will allow you to better prepare for and enjoy it.  

 What Changes When Your Kitten Becomes a Cat? 

As your kitten becomes an adult cat, its overall needs will change along with its size and strength. It’s important to be prepared for the changes before they come so that your cat can enjoy a smooth transition into adulthood. Here are some of the most important changes to be ready for.  


Kitten food has extra nutrients to help smaller cats grow at the right weight and have the nutrients needed to keep up with their high energy. As a cat grows up, they become less active and therefore need less of these nutrients. It’s important to change your cat’s food over to adult food when they are no longer a kitten. Keeping them on kitten food too long can cause them to gain excessive weight, which can lead to health issues.  

 When you’re making the jump from kitten food to adult food, it’s a good idea to slowly transition them over to the new food, mixing them for about a week or so. This process will allow your cat to become used to the different tastes and makeup of the new food, allowing them to be more receptive to the change. The process will also make it less likely that your cat will have any digestive upset over the sudden change in food.  


When you have a kitten, you have a creature on your hands who has a lot of energy. You don’t have to pay too much attention to how much they are moving because they seemingly are moving all the time. As cats age, they tend to play and run around less than they were when they were younger. It’s important to take time to help your cat exercise by either allowing them to go outside safely or playing with them inside the house.  

 An Important Reminder: Reproduction 

Although your kitten isn’t considered an adult cat until a year old, most kittens are able to reproduce at around six months old. This is the approximate age at which your kitten will reach puberty. It’s important to know this because many people assume that kittens can’t reproduce, but that isn’t true. This is why it’s so important to get your kitten spayed or neutered around five or six months old before they show signs of puberty.  

 When a kitten gets pregnant, her body isn’t fully developed to be able to handle the kittens inside of her. Her skeleton won’t be fully grown until closer to ten months to a year old, making for cramped conditions for her growing babies. This can lead to complications for both her and her unborn kittens, especially if she’s pregnant with multiples. That’s why it’s so important to spay and neuter your kittens earlier rather than later.  


Kittens are fun and full of energy. It seems like the kitten stage of your cat’s life goes by quickly, and that’s because it does. Your kitten is considered a cat at just a year old. They will continue to experience growth until about a year and a half old. Knowing these milestones will help you to be prepared for the changes that come as your kitten matures into an adult cat.  


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