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Body mass index

Alternative names



Body mass index (BMI) is a method that can be used to estimate whether you are a healthy weight. Being overweight puts strain on your heart and can lead to serious health problems. These problems include type 2 diabetes , heart disease, high blood pressure , sleep apnea , varicose veins, and other chronic conditions. More than 300,000 lives could be saved in the U.S. each year if everyone maintained a healthy weight!

BMI assesses your weight compared to your height. A healthy BMI for an adult generally falls between 18.5 and 25. If your BMI is more than 25, you are probably overweight. If it is 30 or higher, you are considered obese, and 40 or higher, extremely obese.

You can estimate your BMI by following the steps below.

Steps Example: Someone who weighs 150 pounds and is 5 feet 6 inches tall
1. Convert your weight in pounds to kilograms by dividing by 2.2. 150 lbs. ÷ 2.2 = 68.18 kg
2. Convert your height in feet to inches (1 foot = 12 inches).
5 feet 6 inches = 66 in
3. Convert your height to meters: multiply your height in inches by 2.54.

Then divide by 100.
66 in. x 2.54 = 167.64

67.64 ÷ 100 = 1.68 m
4. Multiply your height in meters by itself. 1.68 x 1.68 = 2.82
5. Divide your weight in kilograms
(step 1) by your height squared (step 4).
68.18 ÷ 2.82 = 24.2
BMI = 24.2

BMI is not always an accurate way to determine whether you need to lose weight. Here are some exceptions:

  • Body builders: Because muscle weighs more than fat, people who are unusually muscular may have a high BMI.
  • Elderly: In the elderly it is often better to have a BMI between 25 and 27, rather than under 25. If you are older than 65, for example, a slightly higher BMI may help protect you from osteoporosis.
  • Children: While an alarming number of children are obese, do not use this BMI calculator for evaluating a child. Talk to your child's doctor about what an appropriate weight is for his or her age.

Doctors use a few different methods to determine whether you are overweight. Your doctor may also take your waist circumference and your waist-to-hip ratio into consideration.

Update Date: 4/8/2003

A.D.A.M. editorial.

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Last updated: Tue, 06 Jan 2009 00:20:03 GMT