Body mass index (BMI) measures body composition. It does this indirectly through a simple calculation relating height and body weight. It estimates body fat and does not measure it directly. BMI provides a valid tool to determine the likelihood someone will be at risk for disease such as hypertension, cardiovascular disease and diabetes, says the American College of Sports Medicine. Calculate a teen's BMI using the same formula as for adults but to determine the likelihood of being over or underweight, a teen's BMI must be compared to other teen BMI's of the same age and sex.
Step 1
Measure the teen's weight in pounds.
Step 2
Measure the teen's height in inches.
Step 3
Convert the weight in pounds to kilograms by dividing by 2.2. Convert the teen's height in inches to meters by multiplying by 0.0254.
Step 4
Square the height measurement.
Step 5
Divide weight by the squared height.
Step 6
Compare the BMI to the appropriate Centers for Disease Control and Prevention (CDC) body mass index-for-age chart (see Resources).
Tips and Warnings
- An example calculation for a 60kg, 1.65m teen follows: 60 / (1.65 x 1.65) = 22.1 When the BMI-for-age is below the 5th percentile, the teen is at risk for being underweight. A BMI-for-age between the 85th and 95th percentile indicates the teen is at risk for being overweight. A BMI-for-age above the 95th percentile indicates the teen is likely overweight.
- BMI is just one tool to estimate body composition and health risks. It should not be the only tool used to evaluate overall health and fitness.
Things You'll Need
- Scale
- Tape measure
References
- "ACSM's Guidelines for Exercise Testing and Prescription"; American College of Sports Medicine; 2000
- Center for Disease Control and Prevention: About BMI for Children and Teens
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