When do domestic cats stop growing?

Domestic cats probably stop growing at around 3 years old. Disappointingly, I have to admit, my reference books on the subject of when domestic cats stop growing are short of information. It is a topic which has been overlooked or perhaps the authors regard it as unimportant. It is believed that the domestic cat's wild cat ancestor, the North African wildcat, are nearly adult in size at about 10 months of age.

Young cat entering the last phase of their growth to adulthood.
Image by DanaTentis from Pixabay.

My observation of my cat, who I raised from a 7-week-old kitten, is that domestic cats stop growing at around 18 months old. But that is a very generalised answer. Frequently, I read online that the purebred cat, the Maine Coon, does not become an adult until they are 4 years old.

And the tiger, yes, I'm referring to the wild tiger, is still putting on muscle at 5 years of age. I'm being very imprecise but perhaps we have to be imprecise because although domestic cats visually stop growing at about 12 months to 18 months of age, they may still be developing and changing towards completed adulthood over the next few years.

So perhaps a better answer is that domestic cats stop growing completely, probably, at around 3 years of age but depending upon whether they are random bred or one of the purebred cat such as the Maine Coon, which I have mentioned.

I notice that the North African wildcat remains in their natal area until they are about a year old which is the age when sexual activity has been observed in captive cats. This means that when the domestic cat's wild cat ancestor leaves their mother's home and becomes independent they are around 1 year of age. That would indicate that they are adult at that age or nearly adult and certainly able to behave independently and survive.

Humans stop growing at about 20% of their lifespan. Domestic cats stop growing at about 17% of their lifespan if we say that they stop growing at the age of 3 and live to the age of 18.