As a cat parent, it's hard not to think of your kitty as a baby, even when they're well into their golden years. Because many cats retain their youthful behavior well into adulthood, it makes you wonder, when are cats full-grown adults and at what age are cats full-grown? Age and breed play a large part in when a kitten becomes a cat.
When Are Cats Full-Grown?
One day, you have a tiny kitten running around your house, and before you know it, they're a big cat. It may seem like they grow overnight, but cats actually go through five life stages, as explained by the American Association of Feline Practitioners and American Animal Hospital Association life stage guidelines. One way to determine when your cat is full-grown is to see into which category they fall into:
- Kitten (birth to six months)
- Junior (six months to two years)
- Prime (three to six years)
- Mature (seven to 10 years)
- Senior and geriatric (11 years and up)
Much like their human counterparts, the development stages of kittens are counted in weeks and months up until the age of two. At what age are cats full-grown? At about one year old. Cats reach adulthood in the junior stage moving into prime stage. You can think of this as your cat being in their late teens and 20s, young adults full of energy and verve.

Once your cat ages into adulthood, your veterinarian can help you determine your cat's ideal weight and recommend a meal plan to help optimize their health. You can work together to modify this plan as your cat moves into each new life stage. It's important to schedule this visit so that these baselines can be established, allowing you to keep an eye on your cat's wellness as they age.
