Typically, kittens should transition to adult cat food at around twelve months. Some larger breeds like Maine Coon and Ragdoll Cats take longer to reach maturity and may transition to cat food around 18 months. The transition should happen over 7 -10 days so their system can adjust to the change. Begin by feeding a mix of ¼ adult food and ¾ kitten food for the first few days. Then transition to ½ adult food and ½ kitten food for a few more days, followed by ¾ adult food and ¼ kitten food. Finally, the diet moving forward can be 100% adult cat food.