At What Age Are Cats Fully Grown?

By PetMD Editorial. Reviewed by Jennifer Coates, DVM on Sep. 29, 2019

Reviewed for accuracy on September 30, 2019, by Dr. Jennifer Coates, DVM

When a child finally turns 18 years old, they are generally considered to be an adult.

But what about our feline family members? At what age are cats fully grown? How do you know when to start feeding them adult cat food?

Your cat will hit several different milestones that signify that she’s becoming an adult cat, but there’s no one magic age where a cat stops growing and maturing.

Although there’s no definitive age, there are general age ranges where most cats generally stop growing and reach adulthood. Here’s what you can expect as your cat makes that transition.

When Do Kittens Stop Growing?

“Kittens usually stop growing at approximately 12 months of age,” says Dr. Nicole Fulcher, assistant director of the Animal Medical Center of Mid-America, although they still may have some filling out to do. “A 12-month-old kitten is equivalent to a 15-year-old person. They are considered full-grown at 18 months of age—which is equivalent to a 21-year-old person.”

Even though many cats stop growing at 12 months, not all cats are done growing at this age. But if they are still growing, it will be at a much slower rate, generally from 12-18 months, so you can expect your cat to be very close to their full adult size at this point. But there may be some cats that can take up to 2 years to be fully grown.

Large breeds, in particular, can take longer. Maine Coons, for instance, might not reach their full size until they are 2 years old or so.

Milestones for Growing Cats

Here are some important milestones for kittens as they become adult cats:

  • Months 3-4: Baby teeth start to fall out and are replaced by adult teeth; this process is usually complete by 6 months of age.

  • Months 4-9: Kittens go through sexual maturation.

  • Months 9-12: A kitten is almost fully grown.

  • 1 year+: Kittens are just reaching adulthood.

  • 2 years+: Kittens are socially and behaviorally mature.

When Should I Feed My Kitten Adult Cat Food?

The right time to transition your cat from kitten to adult food is dependent on many factors. For most cats, around 10-12 months of age is appropriate.

However, a young Maine Coon who is struggling to keep weight on could probably benefit from remaining on kitten food until they are 2 years old or even longer. On the other hand, a kitten who is maturing quickly and becoming overweight on kitten food might benefit from switching at around 8 months of age.

Ask your veterinarian when your cat is ready to make sure you are meeting her nutritional needs.

How Often Should You Feed Kittens?

Most kittens should be fed free-choice until they are around 6 months old because of their high energy requirements.

“From 6 months to a year, an owner can feed three times a day,” says Dr. Jim Carlson, owner of the Riverside Animal Clinic, located outside of Chicago.

After a year, offering meals two times a day will work for most cats, but more frequent, smaller meals may continue to be beneficial for others.

By: Deidre Grieves

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