Calculating your body mass index, or BMI, is a simple way to help you determine whether your weight is healthy based on your height, explains Medline Plus, a service of the National Institutes of Health. Since your BMI does not measure your body fat percentage, it is not always an accurate representation. For example, a highly trained athlete or weightlifter with a lot of muscle mass might have a BMI classified as overweight or obese but not have the health risks typically associated with being overweight or obese, such as type-2 diabetes, high blood pressure and heart disease. Talk to your doctor about your weight if you have concerns.
U.S. System: Method 1
Step 1
Divide your weight in pounds by your height in inches squared.
Step 2
Multiply the result of your division by 703.
Step 3
Round the answer to the nearest tenth to determine your BMI.
U.S. System: Method 2
Step 1
Multiply your weight in pounds by 703.
Step 2
Divide the result by your height in inches.
Step 3
Divide by your height in inches again and round your answer to the nearest tenth.
Metric System
Step 1
Divide your height in centimers by 100 to determine your height in meters.
Step 2
Divide your weight in kilograms by your height in meters squared.
Step 3
Round the answer to the nearest tenth.
Tips and Warnings
- A BMI below 18.5 is considered underweight. A normal BMI is between 18.5 and 24.9. The range for overweight is 25.0 to 29.9, and 30.0 and above is classified as obese, according to the Centers for Disease Control and Prevention.
- Never start a diet or exercise program without speaking to your doctor first. Talk to your child’s pediatrician if you are concerned about his weight. The formula for calculating BMI is not an accurate indicator of a healthy weight for children, warns Medline Plus.
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