How to Calculate BMI for a Kid

Calculating a kid's BMI (body mass index) can help you determine if the kid is at a healthy weight, underweight or overweight. Here's the formula for determining a kid's BMI.

Instructions

• 1

  Weigh the kid and record his or her weight in pounds. For a more thorough reading, weigh the kid a few times to make sure you aren't getting an inaccurate weight.

• 2

  Measure the kid's total height in inches.

• 3

  The formula for determining a kid's BMI is as follows:

  Kid's BMI = [weight / (height x height)] x 703

  Grab a calculator.

• 4

  Multiply the kid's height by itself (height x height) and press the "equals" button. Write down this number as the kid's squared height and press the CC button to clear the calculator.

• 5

  Divide the kid's weight by the kid's squared height and press the "equals" button.

• 6

  Multiply this number by 703 and press the "equals" button. This number is the kid's BMI.

• 7

  Look up the kid's BMI on either a Girl's or a Boy's BMI Chart. Find the kid's age at the bottom of the BMI chart and follow the line up the chart until it intersects with the kid's BMI that you calculated earlier. The curve intersecting with the kid's age and the kid's BMI indicates the kid's BMI percentile.