Body mass index, or BMI, is a number calculated from your weight and height to help assess the amount of body fat you have. Your BMI number can help you determine whether your weight is a health risk. According to the Centers for Disease Control, adults with a BMI between 18.5 and 24.9 are of "normal" weight. Those with a BMI higher or lower than this range are considered overweight and underweight, respectively. If your BMI is higher than 30, you are considered severely overweight.
Step 1
Identify your weight. MayoClinic.com reports that the best time to weigh yourself is the first thing in the morning, and you should do so without clothes or shoes. For purposes of the BMI formula, it doesn't matter whether you weigh yourself in kilograms or pounds.
Step 2
Measure your height. The best way to assess your height is to have someone else measure you with a measuring tape, either in inches or centimeters. If no one else is available, stand next to a wall, place a ruler horizontally atop your head so that it touches the wall. Then slip from beneath the ruler while holding it place, and mark with a pencil the point where the ruler meets the wall. Finally, measure the distance from the mark on the wall to the floor. Be sure to remove your shoes before measuring yourself.
Step 3
Square your height. To square your height, record your measurement in inches or meters and multiply it by itself. For example, if you are 65 inches tall, you will need to multiply 65 by 65. If you measured yourself in centimeters, convert your height to meters by dividing the number by 100, and then square that number. In other words, if you are 165 centimeters, you measure 1.65 in meters. Multiply 1.65 by 1.65 to arrive at the squared number.
Step 4
Divide your weight by your height squared. Record this number. If you have weighed yourself in kilograms and measured yourself in meters, then this number is your BMI number. In other words, BMI = weight (kg) / [height (m) ²]. However, if you weighed yourself in pounds and measured yourself in inches, you still have one more step.
Step 5
Multiply the number received in the previous step by 703. In other words, BMI = weight (lb) / [height (in) ²] x 703.
Things You'll Need
- Scale
- Tape measure
- Ruler
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