How to Calculate Body Mass Index for Kids

Body Mass Index (BMI) is a comparison of height to body weight. It's used in combination with other factors to assess your child's body weight. A BMI chart will provide your child's BMI percentile ranking for age and gender. It should only be used by a physician to make an assessment regarding your child's weight.

Things You'll Need

• Measuring tape
• Scale
• Calculator
• BMI Chart

Show More

Instructions

• 1

  Measure your child's height and weight in metric units. If you measure your child's height in meters and weight in kilograms, you won't have to convert to metric units later.

• 2

  In order to calculate the BMI, divide the child's weight (in kilograms) by the child's squared height (in meters).

• 3

  Use the BMI chart for your child's gender. Consulting the horizontal axis on the chart, locate the hash mark corresponding to your child's age. Follow this mark vertically until it crosses the horizontal line that corresponds to your child's BMI.

• 4

  Locate the point on the BMI chart that corresponds to your child's BMI and age. Compare the vertical position of this point to the percentile curves on the chart in order to estimate the percentile ranking of your child's BMI. A BMI percentile greater than 95 percent is an indication of obesity, while a BMI less than 5 percent is an indication of being underweight.