I used to think that anything over 30 was old, but now that I am over 30 myself, it's all up in the air!! I think you are old when you are unable to do the things that used to bring you joy!! Old is a feeling, not a number...my grandmother was 80 years old when we started talking about putting her in an assisted living facility, and she was ok with it until she went to visit. She came home and told me that she couldn't possibly live there, the place was full of old people!!!