What is BMI?

BMI (Body Mass Index) is used to approximate your percentage of body fat.  It is also used to determine if your weight could be putting you at a higher risk for health problems.

How is BMI calculated?

BMI is calculated by taking your weight in kilograms and dividing by the square of your height in centimeters.

BMI = (weight in kg) / (height in m)²

Example: 70 kg, 175 cm (1.75 m) => 70 /(1.75)² = 22.86

If you prefer English units then you can take your weight in pounds times 703 and divide this by the square of your height in inches.

BMI = (weight in lbs) * 703 / (height in inches)²

Example: 180 lbs, 5′ 10" (70") => 180 * 703 / (70)² = 25.82

How is BMI used?

Adults (>=20 years):

All adults 20 years old or older are grouped into one category. Their BMI is calculated and interpreted directly into the appropriate health risk level. You can use the tool Adult BMI Calculator to determine your BMI and risk level or manually calculate your BMI as explained above.

Child/Teen:

Since the percentage of body fat changes with age in children and with gender a more complicated method is required. First the BMI is calculated just like for adults. However BMI is then compared against a large sampling of kids with the same sex and the same age. This results in a percentile for your kid. The percentile provides a much more accurate indication of how your child compares with all other kids of the same age and gender. The health risk level is then based on the percentile.

You can use the tool Child-Teen BMI Calculator to determine your child’s BMI and risk level or you can manually calculate their BMI and use the Chart to determine their risk level.

What are the health consequences of overweight and obesity for adults?

The BMI ranges are based on the relationship between body weight and disease and death.  Overweight and obese individuals are at increased risk for many diseases and health conditions, including the following:

• Hypertension
• Dyslipidemia (for example, high LDL cholesterol, low HDL cholesterol, or high levels of triglycerides)
• Type 2 diabetes
• Coronary heart disease
• Stroke
• Gallbladder disease
• Osteoarthritis
• Sleep apnea and respiratory problems
• Some cancers (endometrial, breast, and colon)

For more information about these and other health problems associated with overweight and obesity, visit Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults.