How old is a kitten in weeks — and what does each week mean? A kitten's first year is measured in weeks, not years, because it changes so fast: at 4 weeks it is still with its mother, at 8 weeks it is ready for a new home, at 14 weeks it is teething, and at 52 weeks it is near-adult if it is a small breed. This guide is the kitten age calculator by weeks: the weeks-to-months table, what is happening at each age, and how to use it for food, vet visits, and training. Every figure is a guide, because individual kittens vary, and the vet's advice matters more than the table.
The short version is: a kitten is about 4.3 weeks to a month, so 8 weeks is about 2 months, 12 weeks is about 3 months, 26 weeks is about 6 months, and 52 weeks is about 12 months. The first 16 weeks are the most important: the socialisation window, when a kitten learns what is safe and what is frightening, opens at about 3 weeks and closes at about 14 to 16 weeks. A kitten that meets many different people, places, sounds, and surfaces in those weeks, gently and positively, becomes a confident adult — while a kitten kept isolated may stay fearful for life. The kitten weight predictor estimates adult weight from the kitten's current weight and age.
Kitten age calculator by weeks
The table below converts weeks to months and gives the key development at each age. Use it to plan vet visits, vaccinations, feeding, and training — and to know what is normal for your kitten's age.
| Age in weeks | Age in months (about) | What is happening |
|---|---|---|
| 4 weeks | About 0.9 months | Eyes and ears opening; still with mother |
| 6 weeks | About 1.4 months | Weaning begins; first vet visit and vaccinations |
| 8 weeks | About 1.8 months | Ready for a new home; socialisation window opens |
| 10 weeks | About 2.3 months | Learning fast; short play sessions |
| 12 weeks | About 2.8 months | Second vaccinations; exploring more |
| 14 weeks | About 3.2 months | Teething begins; chewing increases |
| 16 weeks | About 3.7 months | Socialisation window closing; keep meeting new things |
| 20 weeks | About 4.6 months | Adolescence begins; testing boundaries |
| 24 weeks | About 5.5 months | About 6 months; near half adult weight |
| 32 weeks | About 7.4 months | About 8 months; growth slowing |
| 40 weeks | About 9.2 months | About 10 months; large breeds still growing |
| 52 weeks | About 12.0 months | About 12 months; most breeds near-adult |
Read the table from top to bottom and the pattern is clear: the first 8 weeks are with the mother, the next 8 weeks are the socialisation window, and the rest of the first year is growth and adolescence. A kitten that is 8 weeks old is ready for a new home, a kitten that is 12 weeks old has had its second vaccinations, and a kitten that is 6 months old is about half its adult weight. The kitten feeding schedule by age guide gives the feeding schedule from weaning to adulthood.
The first 8 weeks: with the mother
The first 8 weeks are spent with the mother and littermates, and they are the foundation of everything that follows. In the first 2 weeks, a kitten cannot see or hear properly, and it depends entirely on its mother for warmth, food, and toileting. By 3 to 4 weeks, its eyes and ears are open, and it starts to explore, play, and eat solid food. By 6 weeks, weaning begins, and the kitten starts to eat solid food regularly. By 8 weeks, it is eating solid food, using the toilet on its own, and ready for a new home.
A kitten should not leave its mother before 8 weeks, and 10 to 12 weeks is better for some breeds: a kitten that leaves too early misses the lessons it learns from its mother and littermates — bite inhibition, social skills, and confidence — and it may be fearful or difficult as an adult. If you are buying a kitten, ask how old it is in weeks, and do not take it home before 8 weeks. The vaccination schedule helper gives the vaccination ages, and the deworming schedule helper gives the deworming ages.
Weeks 8 to 16: the socialisation window
Weeks 8 to 16 are the socialisation window, when a kitten learns what is safe and what is frightening — and what it learns then stays with it for life. A kitten that meets many different people, places, sounds, and surfaces in those weeks, gently and positively, becomes a confident adult. A kitten that is kept isolated, or that has a frightening experience, may stay fearful for life. Socialisation is not about flooding the kitten with new things: it is about short, positive experiences, with treats and praise, and stopping while the kitten is still happy.
Training should start in these weeks too, with short, positive sessions — a few minutes at a time, several times a day — and the basics: name, come, sit, and walking on a lead or using a litter tray. A kitten that is trained with patience and treats will learn fast, and a kitten that is punished will learn fear. The kitten weight chart by age guide gives the growth shares by age, and the how much food should a kitten eat guide gives the calorie tables.
Weeks 16 to 52: growth and adolescence
From 16 weeks, the kitten is growing fast and learning fast, and it enters adolescence at about 5 to 6 months. Adolescence is the testing time: a kitten that was obedient at 12 weeks may ignore you at 6 months, chew things it should not, and push boundaries. That is normal, and it passes — keep training short and positive, keep the rules consistent, and be patient. A kitten that is exercised, trained, and given things to chew will cope with adolescence far better than one that is bored and alone.
By 6 months, a kitten is about half its adult weight, and by 12 months it is about four-fifths or more of its adult weight, when small breeds are near-adult and large breeds are still growing. Feeding changes with growth: a kitten needs three to four meals a day until about six months, then two meals a day, and the amount must be re-checked every two weeks as it grows. The how often should you feed a kitten guide gives the feeding schedule, and the when is a cat fully grown guide gives the growth ages by size and breed.
How to use the weeks table
Use the table to plan vet visits: the first vet visit and vaccinations are usually at 6 to 8 weeks, the second vaccinations at 10 to 12 weeks, and the third at 14 to 16 weeks, with the vet's advice on the exact ages. Use it to plan feeding: a kitten needs three to four meals a day until about six months, then two meals a day, and the amount must be re-checked every two weeks. Use it to plan training: start in the socialisation window, keep sessions short and positive, and be patient through adolescence.
Use it to judge growth, not to worry: a kitten that is a little above or below the rough share for its age is usually fine, as long as it is gaining weight steadily and is bright, eating, and active. What matters is the line over weeks: a smooth, steady rise, not a flat line and not a sudden jump. A kitten that is not gaining weight at all over two weeks, or that is losing weight, needs a vet check. The kitten too skinny — what to do guide covers a kitten that is too thin, and the cat age calculator works out the human-age equivalent for any age.
For related reading, see the kitten weight predictor, the kitten feeding schedule by age guide, the vaccination schedule helper, the deworming schedule helper, the kitten weight chart by age guide, the when is a cat fully grown guide.
Frequently asked questions
How many weeks old is my kitten in months?
A kitten is about 4.3 weeks to a month, so 8 weeks is about 2 months, 12 weeks is about 3 months, 26 weeks is about 6 months, and 52 weeks is about 12 months. Use the table above for any age from 4 to 52 weeks.
When can a kitten leave its mother?
Not before 8 weeks, and 10 to 12 weeks is better for some breeds. A kitten that leaves too early misses the lessons it learns from its mother and littermates — bite inhibition, social skills, and confidence — and it may be fearful or difficult as an adult.
What is the socialisation window for a kitten?
The socialisation window opens at about 3 weeks and closes at about 14 to 16 weeks. A kitten that meets many different people, places, sounds, and surfaces in those weeks, gently and positively, becomes a confident adult. Keep experiences short and positive, and stop while the kitten is still happy.
How much should a kitten weigh at 8 weeks?
As a very rough guide, about a fifth to a quarter of its expected adult weight. A kitten that will be 10 kg as an adult is roughly 2 to 2.5 kg at 8 weeks. Those are rough shares, not measurements — the line over weeks matters more than any single reading.
How often should I feed a kitten?
Three to four meals a day until about six months, then two meals a day. A young animal's stomach is small, so it cannot eat enough in one or two meals to meet its needs, and it needs food little and often. Re-check the amount every two weeks as the kitten grows.
When is a kitten fully grown?
Small breeds finish growing at about 9 to 12 months, medium breeds at about 12 months, large breeds at about 12 to 18 months, and giant breeds at 18 months to 2 years. For cats, most breeds finish at about 12 months, but large breeds such as the Maine Coon can keep growing until 2 to 4 years.
Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.