How many calories does your child need to grow?

In the PICU we focus a lot on nutrition because critically ill children need good nutrition for them to heal from their illness or injury. We often struggle to provide those needed calories. We usually can manage it one way or another, either with high potency oral feedings, special intravenous feedings known as total parenteral nutrition (TPN), or some combination of both of these. We have formulas we use to calculate what a child’s nutritional needs are.

But what about normal children? Many mothers, and it seems most grandmothers, don’t think their children are eating enough to grow. Aside from charting progress in height and weight, how can we calculate if a normal child is getting enough calories?

Here are some good rules of thumb. It’s simplified, but it works. The first thing you must do is determine your child’s weight in kilograms, since that is how we do the calculations: 1 kilogram = 2.2 pounds. Once you know that, you can calculate the average amount of calories needed to grow this way:

• Age newborn to 3 months:  100 calories per kilogram per day
• Age 3 months to 3 years : 90-100 calories per kilogram per day
• Age 3 years to 8 years: 80-90 calories per kilogram per day
• Age 8 years to 12 years: 60-80 calories per kilogram per day
• Age 12 years to 16 years: 45-60 calories per kilogram per day

These calculations assume a normally active child. A significantly more active child needs more. A reasonable rule of thumb for this extra need is for an active child (defined as an hour per day of sustained physical activity) to have about 1.25 times their baseline calories and very active children (defined as more than 90 minutes of sustained physical activity per day) to have 1.5 times their baseline calories.

What does this work out to be in actual numbers? A normal 6-year-old in first grade weighs about 20 kilograms (44 pounds). For him, the daily need is 1700 calories. How about a 17-year-old girl who is a serious soccer player? The average weight for a girl of that age is 55 kilograms (120 pounds), and she needs about 3700 calories; her baseline need is 2400 calories or so, multiplied by 1.5 for her intense activity.

You can find lots of growth charts listing normal heights and weights for children here, and how to use them here.