Q: how many calories should a 13 year old have

A: Don't worry about how much calories you are eating, but instead make sure that those calories come from quality foods and not junk. Always make sure to eat plenty of raw or lightly cooked veggies, fruits, whole grains, healthy fats (like olive oil or dry-roasted nuts), and lean protein. Minimize sweets and junk food. Your body is growing right now and if you give it plenty of healthy nutritious food it'll put it to good use. On the other hand, the more junk you're feeding it, the more likely you'll be to gain fat and have all sorts of health problems down the road. Again, don't worry about HOW MUCH, but instead make sure that WHAT you're eating is healthy.