For that matter, your baby probably won't consume exactly the same amount of food each day. As a general rule, a 7-month old needs 100 calories per kilogram, which equals approximately 2.2 pounds, per day.lthough your baby needs a certain number of calories per pound of body weight, you don't have to drag out the baby scale each morning and figure out how many calories your baby needs that day. Your baby is capable of determining how many calories he needs as long as you offer an adequate amount of food.