How to Calculate Body Mass Index (BMI)

How to Calculate Your BMI and What the Results Mean

Woman measuring her waist
Calculating BMI. Bambu Productions / Getty Images

Definition: BMI is a method of calculating how much you should weigh, based on your height. The BMI is a tool for determining if a person is at a healthy weight, or if they are overweight, the severity of the problem.  

BMI Levels:

  • Less than 18.5 is underweight
  • 18.5 to 25 is considered healthy.
  • 25-30 indicates overweight
  • 30 or greater indicates obesity
  • Morbid obesity is a BMI of 35 if the patient has other serious health conditions, such as diabetes.  If no other health condition is present, a BMI of 40 is considered morbid obesity.

BMI is not accurate in very muscular individuals who may be very heavy for their height, but do not have high levels of fat.

How to Calculate your BMI in 5 steps

1. Convert your weight in pounds to kilograms by dividing by 2.2

2. Convert your height in feet to inches (1 foot = 12 inches).

3. Convert your height to meters: multiply your height in inches by 2.54. Then divide by 100.

4. Multiply your height (in meters) by itself.

5. Divide your weight in kilograms (step 1) by your height squared (step 4). The result of step 5 is your BMI.

It is much easier to use a BMI calculator app, free apps are available for most types of smartphones.  Try an online BMI calculator, which can be found here.

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BMI calculators can be easily found online, 

Also Known As: Body Mass Index

Examples: After calculating her BMI she realized that she did not need to lose weight.

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