Body mass index (BMI) is a method of assessing a person's weight, especially children. Age and sex are essential factors in interpreting the BMI for children since their height is still increasing. You will typically make the measurements required for the BMI in English units and convert them to metric units. You may then use a reference chart to determine the BMI percentile score based on the child's age, gender and metric BMI.
Step 1
Measure your height with a tape measure that uses inches. Assume that your height is 63 inches.
Step 2
Weigh yourself with a scale that uses pounds. Assume that you weigh 110 lb.
Step 3
Calculate your BMI with the formula [W / (H x H)] where W is your weight in pounds and H is your height in inches. This calculation will determine your BMI in units of pounds per square inch (lb/in^2.) For example, a person with a height of 63 inches and a weight of 110 lb. has a BMI of [110 / (63 x 63)] = 0.0277.
Step 4
Multiply your BMI by 703. This will convert a BMI in lb/in^2 to a BMI in kilograms per square meter (kg/m^2.) For example, a BMI of 0.0277 lb/in^2 is equal to a BMI of 0.0277 x 703 = 19.5 kg/m^2.
Step 5
Cross-reference your age and BMI on the correct chart for your gender to obtain your BMI percentile. (See References.) Locate your age on the chart's horizontal line and your BMI on the chart's vertical line. Locate the point on the chart where these two values intersect to obtain your BMI percentile. For example, a 16-year-old girl with a BMI of 19.5 kg/m^2 has a BMI percentile of about 38.
Things You'll Need
- Scale
- Tape measure
- Calculator
- BMI chart
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