The age of a Norwegian Forest Cat can be estimated based on its hair growth. A Norwegian Forest Cat will grow new hair when it is 6 months old, which means it has reached adulthood; white whiskers will grow on its mouth after 6-7 years, when it has entered middle age; when a Norwegian Forest Cat enters old age , white hair will grow on the back of its head, lose its luster, and become rough.

In addition, the age of the Norwegian Forest Cat can also be estimated based on its weight. The weight of an adult cat is 8-11kg. If the weight is much lighter, it means that the Norwegian Forest Cat is not yet an adult.