Ways to Calculate BMI

Having too much body fat, particularly around the middle, puts a person at greater risk for heart disease and stroke. Identifying those in the population at risk for these conditions is an important goal for health professionals and researchers. A simple, low-cost tool, the body mass Index (BMI), which calculates a person's body fat percentage, roughly correlates with a person's level of obesity, which is linked to heart disease and stroke. The formula uses height and weight to calculate a person's percentage of body fat. The calculated result is compared to a chart, which indicates whether someone is overweight, underweight or of normal weight. Although the tool does not measure body fat directly, it is a good, rough tool for assessing someone's risk. Anyone can calculate his or her BMI with a calculator or an online tool (see the Resource for an online calculator).

Standard Measure

• To use pounds and inches, the formula is as follows:

  BMI = weight in lb. / [height in in.^2] x 703

  For example, if your weight is 175 and your height is 70 inches, you would divide 175 by 70^2 and then multiply by 703. This gives a BMI of 25.1, which is slightly overweight.

Metric Measure

• To use metric measures, the formula is as follows:

  BMI = weight in kg / [height in m]^2

  For example, if your weight is 80 kg and your height is 1.8 m, you would divide 80 by 1.8 squared (which equals 3.24) and arrive at 24.7, which is in the normal range.

Calculating BMI for Children

• Calculate BMI for children the same way you do for adults. However, the criteria used to determine obesity are different. Health professionals take a child's age and sex into account when determining whether a child might be categorized as obese.