Mona, I switch from kitten to adult in between six and nine months. You just have to look at the kitten. If he is a good weight and healthy, start mixing in adult food. If he seems to eat more or lose weight, stick with the kitten food a while longer. Staying on kitten food is not a bad thing (like keeping a kid on formula), but it can put on weight and is more expensive. Just my opinion and experience, but I hope I helped!