Doctors use body mass index, or BMI, as a tool to monitor the growth of children. BMI is a calculation that compares a child's height to his weight. Doctors then compare a child's BMI to that of other children on a percentage chart to determine if the child has a healthy weight. Between visits to the doctor, you can calculate your child's BMI yourself to monitor her growth.
Step 1
Stand your child with his back against a wall or doorway. The child should stand up straight with his feet flat on the floor and his chin level. Place a pencil on top of the child's head and mark the wall. Keep the pencil level for an accurate height measurement.
Step 2
Place the end of a tape measure on the floor. Unroll the tape along the wall until you reach the pencil mark. Note the measurement at the mark--this is your child's height.
Step 3
Place your child on a bathroom scale. She should stand straight, and should not lean against a wall or other object. Note the weight reading.
Step 4
If you have noted your child's height in feet and inches, convert the measurement to only inches by multiplying the number of feet by 12 and adding the remaining inches. For example, if your child is 4 feet, 3 inches tall, convert the height to 51 inches.
Step 5
Calculate the square of your child's height in inches. The square of a number is simply that number multiplied by itself. For example, if your child is 51 inches tall, the square of this number, or 51 multiplied by 51, is 2,601. Write down the result.
Step 6
Multiply the child's weight in pounds by 703. For example, if her weight is 55 lbs, the result would be 38,665.
Step 7
Divide the weight calculation by the height calculation. This will give you your child's BMI. For example, if the child is 51 inches tall and weighs 55 lbs, his BMI is 14.86.
Tips and Warnings
- Print out your own BMI percentage chart so you can track your child's growth at home. See the resources section for printable charts. If you are using metric measurements, simply square the child's height in meters, then divide the child's weight in kilograms by the squared height.
Things You'll Need
- Pencil
- Measuring tape
- Bathroom scale
- Calculator
- BMI percentage chart
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