When Is a Kitten Considered Fully Grown?

A spayed or neutered cat may retain kittenlike playfulness into adulthood.
i kitten is playing image by Ramona smiers from Fotolia.com

Your playful kitten will grow into an adult cat rapidly, but don't be fooled by appearances. Some aspects of feline maturity occur more quickly than others. Opting to spay or neuter your cat can make a big difference in how -- and how fast -- your cat grows up.

General Guidelines

In general, a kitten is considered an adult cat when it reaches 1 year of age, but your cat may not actually be fully grown at this point. Kittens typically reach a length and weight close to their full-grown size by 9 to 12 months of age. After the 1-year mark, most cats continue to grow at a much slower rate until at least 18 months of age. Large breeds, such as Maine coon cats, typically take even longer to grow to their full size. These cats may not be fully grown until they reach 2 to 4 years of age.


Sexual maturation in cats, what is essentially puberty in feline terms, takes a few months from start to finish. The process typically begins when the kitten is between 6 and 9 months of age. While a pregnancy is possible once your female kitten starts becoming physically mature, it can be hard on her still-growing body. Male kittens that have reached this age can father kittens of their own, so keep them away from female cats or kittens to avoid this possibility. If you plan to spay or neuter your cat, talk to your vet about when to have the procedure done. Many vets prefer to spay or neuter kittens before they reach full reproductive maturity. Neutering male cats before about 6 months of age may prevent spraying behavior.

Social Maturity

When your kitten reaches about 6 months, he may become more clingy or temperamental because of the hormonal changes going on in his body. By his second birthday, you may notice that your feline companion has become calmer and mellower as he settles into life as a full-grown cat. A spayed or neutered cat may remain more kittenlike than an intact cat, retaining playfulness and a strong need for affection well into old age.


As your kitten matures into an adult cat, his nutritional needs change. Switch your kitten from kitten food to adult cat food at about 12 months of age. You may need to feed your cat less food per day after the first year, especially if you had your kitten neutered or spayed. If you notice your cat developing a pudgy belly, cut back on the amount of food you feed her. Shelters find it more difficult to adopt out an adult cat than a kitten, but an adult cat often makes a good pet because his personality has already been established.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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