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Calculate and Understand Your BMI


Updated February 15, 2014

What Is BMI?

BMI (body mass index) is a screening tool used to measure weight relative to height. While BMI does not measure body fat directly, it has been shown to correlate to measures of body fat, such as underwater weighing, and is considered an accurate alternative for body fat measurement. With a simple formula, you can calculate your own BMI.


How Is BMI Calculated?

To calculate your BMI, you will need to divide your weight in pounds by your height in inches squared and multiply that by 703. The formula is:

weight / [height (in inches)]2 x 703

Consider the following example:

April is 5'5" and weighs 150 pounds. She completed the formula as follows:

  • First, April figures out that her height in inches is 65".
  • Then she calculates that 65" squared (65 times 65) equals 4,225.
  • Next, she divides her weight, 150, by 4,225.
  • The resulting number, which is rounded to 24.96, is April's BMI.


What Does the BMI Number Mean?

Your BMI will place you in one of the following categories:




  • Those with a BMI below 18.5 are considered underweight.
  • Those with a BMI between 18.5 and 24.9 are considered normal weight.
  • Those with a BMI between 25.0 and 29.9 are considered overweight
  • Those with a BMI of 30.0 and above are considered obese.

In addition to BMI, those who have a waist size of more than 40 inches for men, or 35 inches for women, have a higher risk for obesity-related health problems such as diabetes, high blood pressure, and heart disease.

To learn more about how weight-related health risks and BMI, see:
Health Risks and BMI
Health Risks of Obesity

To calculate your BMI online, visit the About.com nutrition Guide's Body Mass Index Calculator.


Centers for Disease Control and Prevention. Healthy Weight: Assessing Your Weight: BMI: About Adult BMI DNPAO CDC. 20 June 2008.

Related Video
How to Calculate BMI
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