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BMI Calculator Requirements

The body mass index (BMI) is a tool to determine the correct height/weight ratio for adults. This measurement is an indirect indicator of a person's body fat. The formula to determine BMI is weight divided by height squared times 703. The BMI number does not always result in an accurate measurement of healthy weight. Some athletes and very fit individuals may be heavier due to muscle mass. For these people, a more correct method to determine body fat is measuring their waist and how much skin/fat can be pinched from their waist.

  1. Obtain the Correct Height

    • For adults, height must be measured in inches. Time of day will affect the measurement of one's height. The spine shrinks during the day and a measurement in the morning maybe greater than a measurement in the evening. The most effective method to measuring height is shoeless and standing straight. Once the correct height is determined it must be squared, multiplied by itself, to get the correct number for the formula.

    Obtain the Correct Weight

    • The most correct weight measurement can be obtained from a digital scale at home or a doctor's scale at the doctor's office. The least amount of clothes possible should be worn. Do not wear shoes of any kind as this will increase weight. Spring-loaded scales risk inaccuracy so should be used with caution. The weight number will be added to the formula without any alteration.

    Requirements for Children BMI Calculation

    • Children require more precise height and weight measurements than adults. Adult measurements can be rounded to the nearest pound or inch. To get the most accurate measurement for children, height must be measured to the nearest 1/8 of an inch. Weight is measured to the nearest decimal fraction.

    Requirements for Measuring With Metric System

    • The BMI calculation formula differs slightly if using the metric system. Determine weight in kilograms and height in centimeters. The height measurement is still squared but the sum of weight times height squared will be divided by 100.

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