what age is a cat fully grown

Cats go through five life stages, and one way to determine when a cat is fully grown is to see which category they fall into. According to the American Association of Feline Practitioners and American Animal Hospital Association life stage guidelines, cats are considered fully grown when they reach the prime stage, which is between three to six years old. However, cats reach adulthood in the junior stage, which is between six months to two years old. Most cats stop growing once they become one year old, which is equivalent to a 15-year-old human. However, some cats can continue to grow in size between the ages of 12 to 18 months, and some breeds, such as Maine Coons, might not reach their full size until they are two years old. Therefore, it is safe to say that cats are fully grown at around 18 months old, which is equivalent to a 21-year-old human.