The same formula is used to calculate body mass index for adults, teens and children. The interpretation of the results, however, depends on different criteria. Normal body fat percentages in children vary according to age and sex, the Centers for Disease Control and Prevention states. Normal body fat in an adult, on the other hand, is less dependent on these variables.
Step 1
Remove your shoes and stand against a wall. Pull your shoulders back and raise your head but don't exaggerate your posture; stand tall but relaxed. Mark the wall at a point the matches the top of your head. Record in inches the distance from the mark to the floor.
Step 2
Weigh yourself using a reliable scale. Remove your shoes and excess clothing. To get an accurate weight reading with which you can compare with future readings, weigh yourself at the same time of day. In the morning after rising is a good time. Record your weight in pounds.
Step 3
Divide your weight by your height in inches squared and multiply the result by 703.?For example, say you are 5 feet, 4 inches tall and weigh 115 lbs. Because your height must be expressed in inches, convert 5 feet, 4 inches to 64 inches. Divide 115 by 4,096 and multiply the result by 705 to arrive at a BMI of 19.7.
Step 4
Compare your result to adult BMI values. You might be underweight if your BMI is less than 18.5 and overweight if it is between 25.0 and 29.9. A value greater than 30.0 suggests obesity. A normal range runs from between 18.5 and 24.9.
Tips and Warnings
- BMI only provides an estimate of body fat. More accurate measurements rely on dual-energy x-ray absorptiometry, called DXA or DEXA, skinfold thickness measurements, underwater weighing, bioelectrical impedance and isotope dilution."
- Use the criteria for evaluating adult and not children BMI values if you are 20 or older.<br /><br /><br /><br />The National Heart, Lung, and Blood Institute warns that BMI may provide a false positive reading of overweight in people with lots of muscle and in athletes. And BMI may not provide an accurate estimate of body fat in anyone who has lost a lot of muscle or in older individuals. Body fat estimates based on BMI may be underestimated in these people.
Things You'll Need
- Bathroom scale
- Yardstick or tape measure
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