Infants cannot tell you if they are feeling hungry or are full. As a parent, it is your responsibility to ensure that your child is getting the proper amount of calories per day. In general, you should feed your young infant when he is hungry, which is known as feeding on demand, notes the KidsHealth website. However, there are some general guidelines if you want to know approximately how many calories he should consume daily.
A general rule for feeding infants is to multiply their weight by 2 1/2 to calculate the number of ounces to feed them in a 24-hour period, according to Babycenter.com. For example, if your newborn weighs 8 pounds, he should eat 20 ounces throughout the day.
Breast milk and formula have on average, 20 calories per ounce, according to Texas Children's Pediatric Associates. This means that an 8-pound infant who is consuming 20 ounces of breast milk or formula a day newborn will have an average of 400 calories daily.
Don't ignore your child's physical cues that she's hungry. These can include opening her mouth and sticking out her tongue, placing her hands, fingers, and fists in her mouth and showing the rooting reflex -- which is when a baby moves her mouth in the direction of something that's touching her cheek. Do not strictly use calculations alone because they only represent averages. Your child may need more or fewer calories a day. Newborns tend to like to eat every two to three hours, which is another guideline you can use in feeding.