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English System
When using the English system of measurement, the BMI formula is:

Weight in pounds (lbs) divided by height in inches (in) squared and multiplied by a conversion factor of 703 (weight (lbs) / [height (in)2] x 703).

Therefore, when calculating BMI, take the weight (lbs) and divide it by height (in). Take the result of that calculation and divide it by height again. Then, multiply that number by 703. Round to the second decimal place.

An example of calculating body mass index using the BMI formula: Weight = 150 lbs, Height = 5'5" (65 inches)

BMI Calculation: [150 ÷ (65)2] x 703 = 24.96

## Understanding the Results

For adults 20 years old and older, the BMI results are interpreted using standard weight status categories that are the same for all ages and for both men and women. The standard weight status categories associated with BMI ranges for adults are shown below:

 BMI Weight Status Below 18.5 Underweight 18.5 – 24.9 Normal 25.0 – 29.9 Overweight 30.0 and Above Obese

For children and teens, after calculating the BMI, the BMI number is plotted on the BMI-for-age growth charts (for either girls or boys) to obtain a percentile ranking. The percentile indicates the relative position of the child's BMI number among children of the same sex and age.

BMI-for-age weight status categories and the corresponding percentiles are shown in the following table:

 Weight Status Category Percentile Range Underweight Less than the 5th percentile Healthy weight 5th percentile up to the 84th percentile At risk of overweight 85th to less than the 95th percentile Overweight Equal to or greater than the 95th percentile

However, BMI is just one measure to assess the risk associated with weight.

(Click BMI and Weight for more information on what other factors healthcare providers consider when determining risk for certain medical conditions related to weight.)

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