When Do Cats Stop Growing? Kitten Growth by Month

When do cats stop growing? For most cats, at about 10 to 12 months old. Kittens do most of their growing in the first six months, then slow down and fill out. Large breeds can keep adding muscle for longer, but the big changes are over by the first birthday.

This post walks through the growth timeline, what adult weight to expect, and how to feed a kitten as it nears adult size. To see your kitten’s age in human years at any point, use our cat age calculator.

How fast do kittens grow?

VCA’s guide to feeding growing kittens gives three useful markers: kittens are usually weaned at about 8 weeks, reach about 80% of their adult size by 30 weeks, and are close to adult size by about 40 weeks. After that, growth is slow filling out rather than getting taller or longer.

Age	Growth stage	Human years (AAFP)	Food
0–8 weeks	Nursing, then weaning at about 8 weeks	Up to about 3	Mother’s milk, then kitten food
2–4 months	Fastest growth; baby teeth all in	About 2–6	Kitten food, 3–4 meals
4–7 months	Adult teeth come in; about 80% of adult size by 30 weeks	About 6–11	Kitten food, 3 meals until 6 months
7–10 months	Slowing; near adult size by about 40 weeks	About 11–13	Kitten food, 2 meals
10–12 months	Growth ends for most cats	About 13–15	Switch to adult food at about 1 year
1–2 years	Large breeds may keep filling out	15–24	Adult food, portions by body condition

Growth markers from VCA; human years from the AAFP chart (points between chart values are interpolated by our calculator); meals from Cornell and VCA.

How old is a 6-month-old cat?

A 6-month-old kitten is about 10 in human years on the AAFP chart, roughly a child entering adolescence. It is usually around three-quarters of its adult size, has most of its adult teeth, and is still growing. It still needs kitten food.

Here is a worked example with our calculators. A 5-month-old kitten weighs 5 lb:

• Age: enter 0 years and 5 months in the cat age calculator and it returns about 8 human years.
• Calories: enter 5 lb and choose the kitten option in the cat calorie calculator. It works out the resting energy for 2.27 kg and multiplies by 2.5 (the Merck kitten factor), giving about 323 kcal a day, with a range of about 291–356.

That is a lot for a 5 lb animal: about the same as a 13 lb neutered adult cat needs. Growth is expensive, which is why kittens eat so often.

How big will my cat get?

There is no reliable growth-curve formula for cats like there is for puppies. Breed and sex matter most. A German study weighed 539 pure-bred and 75 non-pedigree adult cats at cat shows and vet clinics. Using only cats at ideal body condition (score 5 of 9), it grouped breeds into five size classes with these average weights:

Breed size group	Example	Females	Males
Very light	Siamese, Oriental Shorthair	6.2 lb (2.8 kg)	7.9 lb (3.6 kg)
Light	—	7.1 lb (3.2 kg)	9.3 lb (4.2 kg)
Medium	—	7.7 lb (3.5 kg)	9.5 lb (4.3 kg)
Large	Norwegian Forest, Siberian	8.8 lb (4.0 kg)	11.2 lb (5.1 kg)
Giant	Maine Coon	10.8 lb (4.9 kg)	13.4 lb (6.1 kg)

Source: Kienzle and Moik, British Journal of Nutrition 2011. Pounds converted by us.

Two things stand out. Males are heavier than females in every group, by about 1.5 to 2.5 lb. And even “giant” cats at ideal condition average well under 15 lb, so a 16 lb domestic shorthair is far more likely to be overweight than big-boned. Our post on how much a cat should weigh covers how to check that with a body condition score.

Do large breeds like Maine Coons grow longer?

Larger breeds tend to keep filling out after their first birthday. Maine Coon owners and breeders often say their cats take a few years to reach full size, but we couldn’t find a peer-reviewed growth study that confirms a specific age, so treat that as experience rather than a measured fact. What is well established is that by about a year, the skeleton has done most of its growing in all cats, and extra weight after that is mostly muscle or fat.

When should kittens switch to adult food?

The 2021 AAHA nutrition guidelines place the switch from a growth diet to adult food at about 12 months for cats. A few practical points:

• Meals: Cornell suggests three meals a day until 6 months, then two meals a day from 6 months to a year. Our post on how much a kitten should eat has a calorie chart by weight.
• After neutering: calorie needs drop. A neutered adult cat needs only about 1.2 × its resting energy, less than half of the kitten factor. Keep feeding kitten food until about 12 months, but weigh your kitten every couple of weeks and trim portions if it starts to look round.
• Switch gradually: mix the new food in over about a week to avoid an upset stomach.

Once your cat is an adult, the cat food calculator turns its weight into daily cans and cups.

Why do so many cats get fat after their first year?

The Kienzle study found that half of neutered males and 38% of neutered females in its sample were overweight. The first year sets the pattern: kittens are fed generously, growth stops, neutering lowers energy needs, and the portions don’t change. Weigh your cat monthly through the first two years and keep a note. A slow upward creep after 12 months is fat, not growth.

When to call your vet

Growth varies, but talk to your vet if your kitten:

• is not gaining weight from week to week, or loses weight
• is much smaller than littermates and seems weak or tired
• has a swollen belly with thin limbs, diarrhea or vomiting (worms are common in kittens)
• still has baby teeth alongside adult teeth after about 7 months
• seems to be gaining fat quickly after neutering

If you are unsure how old a rescued kitten is, our post on how to tell how old a cat is shows how to read the teeth.