Has the kitten who used to nap in the crook of your neck turned into a full-fledged winter scarf? They won’t keep growing forever! Most cats stop growing and reach their full adult size between 12 and 18 months old. Some larger breeds, however, continue growing and filling out for another two to four years.

Key points

• Most cats reach their full size around their first birthday.

• Breed plays the biggest role in how long your cat will continue growing, but gender, genetics, spaying or neutering, and nutrition all shape how big your cat gets.

• Kittens grow fastest in their first few months, then growth slows down before it stops.

When do cats stop growing, by breed

Breed has one of the biggest influences on your cat’s growth timeline. Big breeds like the Maine Coon and Norwegian Forest Cat may keep growing until 2 years or more. Ragdolls often don't reach full size until around age 4. 

Here’s when some of the most popular breeds typically reach their full adult size.

	Age fully grown	Typical adult weight
Singapura	9 – 12 months	4 – 8 lbs
American Shorthair	12 – 18 months	10 – 15 lbs
British Shorthair	12 – 18 months	7 – 17 lbs
Persian	12 – 18 months	7 – 12 lbs
Siamese	12 – 18 months	8 – 12 lbs
Bengal	18 months – 2 years	8 – 15 lbs
Norwegian Forest Cat	2 – 3 years	12 – 16 lbs
Maine Coon	2 – 4 years	Males: 18 – 25 lbs;  females: 10 – 14 lbs
Ragdoll	3 – 4 years	10 – 20 lbs
Savannah	Up to 3 years (varies by generation)	12 – 25 lbs+

What affects how big your cat gets

Your cat's final size isn't set by breed alone. Here’s what influences how large your cat will become.

Gender

Male cats are generally larger and heavier than females of the same breed. While this difference is modest in many breeds, it’s much more pronounced in Maine Coons, where adult males can outweigh females by 10 pounds or more.

Females also tend to reach their full size a bit sooner. Female cats often finish growing around 10 to 12 months, while males may keep growing until closer to 18 months.

Spaying or neutering

Spaying or neutering may delay the closure of your cat’s growth plates, allowing bones to grow for a little longer. Research following kittens neutered before 19 weeks of age found they followed a slightly different growth pattern, but breed and genetics remain much stronger predictors of adult size.

A cat’s growth, therefore, is not an important factor in deciding the best time to spay or neuter a cat. Most vets and the American Veterinary Medical Association support spaying or neutering cats by 5 months of age. 

Genetics

Genetics set the blueprint for your cat's frame and size. The best predictor is often the parents. If you know how big your kitten's mom and dad are, you have a solid clue to your little one's adult size.

Diet and nutrition

Good nutrition helps your kitten grow and develop properly, but it won’t make them larger than their genetics allow. Feeding a complete and balanced kitten food during their first year supports healthy bone, muscle, and brain development. Once your kitten reaches adulthood, you can transition them to an adult diet based on your veterinarian’s recommendations. 

Our kitten feeding chart can help you feed the right amount at every stage.

Birth size

A kitten’s birth weight doesn’t necessarily predict their adult size. Kittens born smaller than their littermates, including runts, may grow more slowly at first, but many experience catch-up growth during their first weeks and months of life. Once they’re healthy and growing normally, breed and genetics become much stronger predictors of adult size than birth weight.

Cat Growth Chart: What to Expect at Every Age

Age	Growth stage	What to expect
Birth–8 weeks	Newborn	The fastest growth of your kitten’s life. Healthy kittens gain about 10 to 15 grams per day and typically reach around 2.2 pounds (1 kilogram) by 8 weeks.
2–6 months	Kitten	Rapid bone, muscle, and organ development continues. Baby teeth are gradually replaced by adult teeth, and most kittens reach about 75% of their adult weight by 6 months. Many cats reach sexual maturity around 6 months, so talk to your vet about spaying or neutering if you haven't already.
6–12 months	Adolescent	Growth becomes more gradual as your kitten starts looking more like an adult cat. Most average-sized breeds are close to their adult height and length by their first birthday, though they may continue filling out.
1–4 years	Young adult	Most cats reach their full adult size between 12 and 18 months. Large breeds like Maine Coons and Ragdolls continue gaining muscle and body mass until they’re 2 to 4 years old.
10+ years	Senior	Growth is complete. Cats are generally considered senior at 10 years old, and the focus shifts from growing to maintaining a healthy weight and body condition through proper nutrition, exercise, and regular veterinary care.

Every kitten grows at their own pace. While breed and genetics largely determine when your cat reaches their adult size, keeping your cat at a healthy weight is just as important as tracking their growth. Not sure how heavy your cat should be? Check in with your vet to make sure your cat is right where they should be.

How to Tell When Your Cat Is Fully Grown

Every kitten grows at their own pace. While breed and genetics largely determine when your cat reaches their adult size, healthy nutrition, routine veterinary care, and plenty of play help support normal development along the way. Before you know it, that tiny kitten curled up in the crook of your neck will be a full-grown cat  –  who may still insist on being carried around on your shoulder like a kitten.

FAQs about when cats stop growing

At what age is a cat fully grown?

Most cats are fully grown between 12 and 18 months old. Average-sized breeds usually finish by around their first birthday. Large breeds like Maine Coons and Ragdolls can keep growing for a couple of years, and Ragdolls may not finish until about age 4.

How much do cats grow after 6 months?

Quite a bit, but slower than before. By 6 months your kitten has done most of their fastest growing. From there, they keep gaining size and muscle at a gentler pace until they reach their full adult frame, usually between 12 and 18 months.

Can you tell how big a cat will get?

Not exactly, but you can get a good estimate. Breed and the size of your kitten's parents are the best clues to adult size. Paw size and other old wives' tales aren't reliable predictors, so when in doubt, ask your vet.

Why does my 1-year-old cat still look like a kitten?

Some cats simply take longer to fill out. Large and slow-maturing breeds keep growing well past a year, so a lean, kitten-like look at 12 months can be normal. If you're worried about your cat's weight or development, check with your vet.

When do kittens stop growing?

Kittens stop growing when they reach their full adult size, most often between 12 and 18 months. Growth is fastest in the first few months, then slows steadily. Large breeds are the exception and can keep growing for up to 2 years or more.

How big is the average cat?

The average adult domestic cat weighs about 8 to 12 lbs, with many landing near 10 lbs. Males are generally larger than females. Breed, build, and body condition all affect where your cat falls in that range.