How to calculate Body Mass Index (BMI)

The Body Mass Index (BMI) is a measure to determine how your weight compares to your height. For example, 150 pounds might be overweight for someone who is 5 feet tall, but underweight for someone who is 6'6" tall. Here's how to calculate your BMI.

Measure your height in feet and inches. For example, 5'9".
Multiply the number of feet by 12 and add it to the number of inches to get your height in terms on inches only. For example 5'9"=5*12+9=60+9=69 inches.
Take your weight in pounds. For example, 150 pounds.
Multiply your weight by 703. For example 150*703=105450.
Then divide the result by your height in inches. In our example 105450/69=1528.26087
Then divide that result by your height in inches again. In our example, 1528.26087/69=22.15
A BMI under 18.5 is considered underweight, between 18.5 and 24.9 is normal, between in 25 and 29.9 is overweight, and above 30 is obese. However, depending on your body makeup, the information may be limited. For example, a very muscular individual may have a high BMI but have no excess body fat. Talk to your doctor about other useful measurements, such as waist circumference.
Alternatively, you can use an online BMI calculator like the one linked to in the resources section.

  • This is not medical advice. Talk to your doctor about your medical concerns or before starting a diet or exercise program.

Copyright 2009 by Michael Nehring