Kitten Development Stages: When Is A Kitten Fully Grown?

Cats can breed nearly all year round, but kitten season runs from April until late autumn. This is the time when cats predominantly tend to breed and give birth.

We’ve taken a closer look at how kittens grow and develop, to help answer the most common questions. From when kittens first open their eyes to the age at which they become an adult cat, this guide should help you understand the various stages of kitten development. And if you’re thinking about getting a kitten, make sure to check out our kitten checklist! It’s full of all the information and handy tips you should know when adopting a kitten. 


Natusan cat


When are kittens fully grown?


A cat is considered an adult from one year old, but cat adolescence lasts until the age of 18 months - so your adult cat might still act like a kitten and may even have a bit more growing to do, depending on their breed. By 18 months, cats will mature and settle into adulthood.


A kitten's first month


Kitten development happens incredibly quickly in the first month, with changes happening all the time.


The first 2 weeks

Kittens are born with both their eyes and ears closed, so for the first 1-2 weeks of their life they are blind and deaf. Their sense of smell helps them know where their mum is. Kittens at this stage will spend most of their time sleeping and huddled together, with regular feeds from mum - usually every couple of hours or so, day and night. 


At 2 weeks old

This is when a kitten’s eyes will finally open. Their eyesight can take a while to develop, so it’s recommended to keep them away from bright lights at first. All kittens are born with blue eyes, but eye colour can change in the coming weeks. Kittens will also start to grow teeth between when they’re around 2-4 weeks old - but they won’t have a full set of baby teeth until about 8 weeks old. 

2 weeks also marks the start of the socialisation period, a vital period in kitten development. From 2-7 weeks, while kittens’ brains and sensory systems are developing, they are learning from all their environments and interactions. Positive experiences during this time will help them to learn that these things (and people!) are non-threatening, and it’s key to a happy and well balanced cat in later life.


At 3 weeks old

At 3 weeks, a kitten’s ears also start to open up, allowing them to hear. While kittens can make small sounds from birth (usually to let mum know they’re hungry!) this is the age at which they’ll start purring - and they’ll become more vocal as they grow. Kittens will also start to take their first wobbly steps at around 3 weeks of age.


At 4 weeks old

With a full set of senses developing - and having learned to walk more confidently - kittens will start to explore at 4 weeks old. At this stage in the growth of a kitten, it’s probably time to start kitten-proofing things around the house, so take a look at our guide to cat-proofing your home!

It’s also at around this time in kitten development that they can be introduced to the litter box. Kittens can learn a lot just by watching their mum, but it might take them a little while to get the hang of things while they’re learning!


Natusan cat


The second month of kitten development


Week 5

From 5 weeks old, some kittens start showing an interest in their mum’s food. They can be introduced to kitten food, but their mum will carry on nursing them for a few more weeks. This gradual process will help them get used to solid food. 


Weeks 6-8

As we’ve covered from week 2, socialising is a vital part of kitten care, helping them grow into a well-adjusted adult. Continue to socialise kittens to get them used to a range of surroundings, sounds and people, as week 7 marks the final week of what is considered to be the kitten’s socialisation period. 


Natusan cat


The third month


While weaning can start from week 5, kittens should be fully weaned onto kitten food by the age of 9 weeks. As they now have a full set of baby teeth, they can eat either dry or canned kitten food - which is extra high in protein and fat for growing kittens.

A kitten’s first set of vaccinations should be done at around 9 weeks of age. From here, your vet will inform you about the timeline of further vaccinations.

There’s another set of important vaccinations at 12 weeks of age - and this is also a good time to discuss neutering, which will come slightly later. It’s recommended that kittens are neutered at around 4 months old, after their vaccinations.


Natusan cat

When can kittens be rehomed?

Kittens can be rehomed from the age of 12-14 weeks, and it’s recommended they stay with their mum and littermates until this age for the best physical and behavioural development.

During their third month (from the age of 8-12 weeks) kittens are still learning the basics of being a cat, mostly from their mum. Everything from how to communicate and play with other cats to how to use the litter box will be picked up from watching their mum in action, and spending time with their littermates. 

In order for a kitten to learn all it needs to know to be a healthy happy cat, it’s recommended that kittens stay with their mum and siblings until they’re 12-14 weeks old.


Natusan cat

When can kittens be let outside?

Once a kitten has been both vaccinated and neutered, it’s safe for them to have supervised access outside. It’s best to keep an eye on them, and make sure they seem confident enough in the house before letting them explore the garden!


How can you tell how big a kitten will get?

At the age of 16 weeks a kitten will reach about half of their final adult weight - so if you weigh them at this point, simply double it and you’ll have a good guide for their adult size. A kitten’s breed, gender, and general lifestyle can also impact their full adult size and weight.


Now you have an understanding of when kittens are fully grown, and how they develop through their first months of life, you’ll be better equipped to support and raise well-adjusted, happy kittens into their adult life - and have a lot of fun along the way. 

If you want to learn more about kittens and how to support their development, take a look at our guide on how to litter train a kitten




At what age do kittens calm down?

Most kittens calm down between the ages of 6 to 12 months, and by 18 months they’ll have reached maturity. 


Is a 6 month old kitten fully grown?

No, a 6 month old kitten still has a way to go until they’re fully grown. At 6 months, they’re entering adolescence, a bit like a human teenager, and will stop growing between 12 to 18 months of age.


Do kitten paws indicate size?

No, a kitten’s paw size is not an indication of how large they will grow. 


How do you tell if a kitten will grow up to be friendly?

A kitten that has been well socialised during the socialisation period, from 2 weeks to 7 weeks old, is likely to grow up friendly and happy. Positive exposure to people and environments in this time will help kittens grow into well-adjusted cats.





16/03/2022 by NatuTeam

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