How do you calculate your BMI long-hand?


Quick Answer

To calculate your body mass index, divide your weight in pounds by your height in inches squared, then multiply the quotient by 703. Those who use the metric system may divide weight in kilograms by height in meters squared; the quotient is the BMI. Use a BMI chart to determine whether the number indicates underweight, healthy weight, overweight or obese. Those with a BMI between 18.5 and 24.9 are generally considered to be a healthy weight.

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Full Answer

An increase in abdominal fat can lead to health problems. To determine whether you are at risk for diseases such as diabetes, dyslipidemia, hypertension or cardiovascular disease, measure your waist circumference as well as your BMI. Wrap a measuring tape around your abdomen, making sure the tape lies over your hip bones. Use an overall health risk and obesity class table to determine whether the measurement indicates increased risk. For males, a healthy waist-to-hip ratio is .95 or less; for females, .80 or lower.

You can measure body fat percentage using calipers or other instruments of measure; however, you may also use a formula to determine the rough percentage. This formula differs for men and women, and is most accurately determined in the morning. The women's formula has five factors, which are calculated by measuring parts of the body, including the forearm, wrist, waist and hip.

The fifth factor is total body weight times 0.732, with 8.987 added to the product. Add the five factors together to determine lean body mass. Next, calculate body fat weight, which is total body weight minus lean body mass; finally, multiply body fat weight by 100, and divide the product by the total body weight. The quotient is your body fat percentage. The men's formula differs slightly, as it only uses a waist measurement.

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