Cats stop growing at around 1.5-2 years of age, usually, but the answer depends on what you mean by “stop growing” and don’t be too precise. You don’t get a clear answer on the internet and my books don’t help. In addition, some cat breeds are said to stop growing later than the average for random bred cats. I’m referring to the Maine Coon, which they say becomes an adult cat at about 4 years of age but this probably includes bulking up.
It would seem that the bones of a cat stop growing at about 12 months of age. The cat continues to mature and develop by putting on bulk, meaning muscle, for a further 6 to 12 months.
You could say, therefore, that the cat stops growing at about 1 to 2 years-of-age. I don’t believe it is a good idea to be too strict about a timetable because it is not entirely predictable as to when a cat stops growing.
If you work it out by reference to the time when humans stop growing, which is about 21 years of age, divide that by 7 and you get 3 years of age for a cat. That however is not a very good calculation because a comparison between a cat’s age and a human’s age is not linear by which I means the mathematical relationship between the two ages varies during the lifetime.
Various sources provide various answers, which is slightly perturbing. Another website says that a cat’s bones stop growing at about 8 months-of-age and they reach sexual maturity at 12 months-of-age.
Yet another website says that when your cat is 12 months of age he’ll be the equivalent of a 15-year-old teenage human. Your cat will continue to grow for another 12 months. So according to this website (the about.com website) a cat stops growing at 24 months-of-age.
As mentioned, cats stop growing at around 1.5-2 years of age, usually. The cat may continue to develop and change shape after growth has ceased and therefore they don’t become adults until that additional phase has completed. Some cat breeds may stop growing beyond that time, as mentioned. “Growing” may include maturing and developmental growth.